HR Organization Question

Hello,

We are facing some errors due the following situation. We have 3 HR Organizations, but we have centralaized the Finance department, the requisition are created by one person that belongs to one of this HR organization on belhaf the other 2. The problem is that whe the user forgets to change the Legal Entity in the charge account. the requisition gets into PO and AP with out giving any errors... and the problem is identified when the AP department runs create accounting... and cant create account.  I tried to create a security rule to avoid the user to continue with