<Page>

                                                                   EXHIBIT 10 B1

                  CERTIFICATION OF PRINCIPAL EXECUTIVE OFFICER

                                 CERTIFICATIONS

I, Ronald E. Robison, certify that:

          1.  I have reviewed this report on Form N-CSR of Morgan Stanley
Mid-Cap Value Fund;

          2.  Based on my knowledge, this report does not contain any untrue
              statement of a material fact or omit to state a material fact
              necessary to make the statements made, in light of the
              circumstances under which such statements were made, not
              misleading with respect to the period covered by this report;

          3.  Based on my knowledge, the financial statements, and other
              financial information included in this report, fairly present in
              all material respects the financial condition, results of
              operations, changes in net assets, and cash flows (if the
              financial statements are required to include a statement of cash
              flows) of the registrant as of, and for, the periods presented in
              this report;

          4.  The registrant's other certifying officers and I are responsible
              for establishing and maintaining disclosure controls and
              procedures (as defined in Rule 30a-2(c) under the Investment
              Company Act of 1940) for the registrant and have:

          a)  designed such disclosure controls and procedures to ensure that
              material information relating to the registrant, including its
              consolidated subsidiaries, is made known to us by others within
              those entities, particularly during the period in which this
              report is being prepared;

          b)  evaluated the effectiveness of the registrant's disclosure
              controls and procedures as of a date within 90 days prior to the
              filing date of this report (the "Evaluation Date"); and

          c)  presented in this report our conclusions about the effectiveness
              of the disclosure controls and procedures based on our evaluation
              as of the Evaluation Date;

          5.  The registrant's other certifying officers and I have disclosed,
              based on our most recent evaluation, to the registrant's auditors
              and the audit committee of the registrant's board of directors (or
              persons performing the equivalent functions):

<Page>

          a)  all significant deficiencies in the design or operation of
              internal controls which could adversely affect the registrant's
              ability to record, process, summarize, and report financial data
              and have identified for the registrant's auditors any material
              weaknesses in internal controls; and

          b)  any fraud, whether or not material, that involves management or
              other employees who have a significant role in the registrant's
              internal controls; and

          6.  The registrant's other certifying officers and I have indicated in
              this report whether or not there were significant changes in
              internal controls or in other factors that could significantly
              affect internal controls subsequent to the date of our most recent
              evaluation, including any corrective actions with regard to
              significant deficiencies and material weaknesses.

          Date: October 20, 2003


                                              Ronald E. Robison

                                              Principal Executive Officer

<Page>

                                                                   EXHIBIT 10 B2

                  CERTIFICATION OF PRINCIPAL FINANCIAL OFFICER

                                 CERTIFICATIONS

I, Francis Smith, certify that:

          1.  I have reviewed this report on Form N-CSR of Morgan Stanley
Mid-Cap Value Fund;

          2.  Based on my knowledge, this report does not contain any untrue
              statement of a material fact or omit to state a material fact
              necessary to make the statements made, in light of the
              circumstances under which such statements were made, not
              misleading with respect to the period covered by this report;

          3.  Based on my knowledge, the financial statements, and other
              financial information included in this report, fairly present in
              all material respects the financial condition, results of
              operations, changes in net assets, and cash flows (if the
              financial statements are required to include a statement of cash
              flows) of the registrant as of, and for, the periods presented in
              this report;

          4.  The registrant's other certifying officers and I are responsible
              for establishing and maintaining disclosure controls and
              procedures (as defined in Rule 30a-2(c) under the Investment
              Company Act of 1940) for the registrant and have:

          (i)   designed such disclosure controls and procedures to ensure that
                material information relating to the registrant, including its
                consolidated subsidiaries, is made known to us by others within
                those entities, particularly during the period in which this
                report is being prepared;

          (ii)  evaluated the effectiveness of the registrant's disclosure
                controls and procedures as of a date within 90 days prior to the
                filing date of this report (the "Evaluation Date"); and

          (iii) presented in this report our conclusions about the effectiveness
                of the disclosure controls and procedures based on our
                evaluation as of the Evaluation Date;

          5.  The registrant's other certifying officers and I have disclosed,
              based on our most recent evaluation, to the registrant's auditors
              and the audit committee of the registrant's board of directors (or
              persons performing the equivalent functions):


<Page>

          a)  all significant deficiencies in the design or operation of
              internal controls which could adversely affect the registrant's
              ability to record, process, summarize, and report financial data
              and have identified for the registrant's auditors any material
              weaknesses in internal controls; and

          b)  any fraud, whether or not material, that involves management or
              other employees who have a significant role in the registrant's
              internal controls; and

          6.  The registrant's other certifying officers and I have indicated in
              this report whether or not there were significant changes in
              internal controls or in other factors that could significantly
              affect internal controls subsequent to the date of our most recent
              evaluation, including any corrective actions with regard to
              significant deficiencies and material weaknesses.

          Date: October 20, 2003


                                              Francis Smith

                                              Principal Financial Officer