user exit during conversion from Planned Order to PR

Dear SAP gurus,

In our project, the PR release strategy will be triggered by value in requisitioner field, in which this filed will be filled by department code. However we find out that during Planned Order conversion to PR, the requisitioner is automatically filled by user id that doing the conversion.

Is there any user exit that can be triggered in this process where we can put our own code so the requisitioner can be filled with the correct requisitioner code, thus our release strategy can be triggered as well?

Best regards

John.