3816245 - How do I assign an Exception Message to a custom Audit rule?

When I go to Administration > Expense > Expense Admin > Audit Rules, find the Audit Rule and click Modify, on the third step of the wizard, I can see the current Exception assigned to the Audit Rule, but it seems I cannot replace it. The fields Exception Code, Exception Level and Exception Text are greyed out and if I hover over them with the cursor, a little blocking sign appears:

I would however need to replace the current message with a new Exception that I have already created.

I have created a new Exception via the Exceptions tool in Expense Admin and I would like to assign it to an existing Audit rule. , KBA , CON-CA-ADM , Administration , Problem