Not able to edit the trip exps

I have an issue in travel management. Can u pls help me out in this issue?

The issue is, employee has posted trip exps in TR05settled in PREC (mass settle)Posting run in PRFI. Till here, the status was showing as u201Ctrip approved & transferred to FIu201D in PR05. But, afterwards, employee wants to make some changes on his/her trip. So then he went to PRRW and rejected the trip. Now, the status has been changed to u201Ctrip approved & settledu201D in PR05. When user attempts to edit the trip line he gets a message u201Cunauthorized to make any changesu201D. I know this seems to be a security issue but is there a way in SAP to edit the trip exps made by him.

Thanks