Category expense account goes back to zero when ordering for another entity

Hi,

We have costing set up on the HR record for each employee. We also use expense account rules. If a user creates a requisition for an entity that is not the same as the entity on her HR record, she gets an error saying that the charge account needs to be entered. The account number generated by the expense account rule for the category goes back to zero. How do I change that so that the expense account remains and the user just needs to change the entity number?

Thanks

Linda