Request Ledger Close and the Two Options Close and Undo

Dear All

We are using PSFSCM 9.2 image 0 PT 8.53, could anyone guide how to allot only one option either of Close or Undo to One user and the other to the other. LIve example, is Mr. A is authorized to execute only Close request to close the financial year in question while if Undo is needed it should not be executed by Mr. A the authorized person to execute Undo so that the ledger closing is reversed is Mr. B. So, kindly guide how to achieve this to provide one option to one person only at a time though both