iProcurement and Project related Requisition entry...

Hello -

In iProcurement when users enter a project related requisition, the accounting flexfield information will be populated based on the project number they have entered. 

However, some of our iProcurement users enter requisitions using an account number (within an accounting flexfield) that is specifically and only to be used when entering a project related requisition - but they do not fill in the project information.

This is causing us grief.

My question is... Can we create a security or validation rule that stops users from using a specific account number if they have not entered project information in the Projects tab.