How to create a accounting map using different subledger applocation in the input?

Hi,

Does anyone know if we can create a mapping set using a different subledger application in the input? E.g: I am configuring the accounting rule for requisition change account (subledger application: purchasing) and I need to create a mapping set that will look into the work order DFF as input, that field is in cost accounting subledger application.

I have set it up but when I create a requisition from a WO, it doesn't read and give an error as the charge account is blank.

Thanks

Luisa