Credit note with a restocking fee

We have come across a situation where we had to return a job related item to the vendor and that process went smoothly.  Issue being there is a restocking fee that needs to be expensed to a different GL account on the credit note we are trying to apply to the return.  I have not been able to find a good way to do this at all.  Could anyone give me step by step instructions or at least a good idea of how I can accomplish this?  Would we need to add the restocking fee to the PO?  I am really at a wall here.  I have read the entire purchase order users manual and its not mentioned anywhere how to accomplish this.  PLEASE HELP ME!!!!