AME Approval Limit Validation

We are configuring AME for iExpense that will follow the employee supervisor hierarchy and the approval limit assigned to the employees will be maintained in a lookup. We will be using 'chain of authority using a approval group'. The approval group will use a dynamic query to find the supervisor id. Now the level of approvals will depend on the dollar amount of the expense report and the approval notification has to progress sequentially, so it can be one, two or any level.

The question is that since the dollar amount is maintained in a lookup how will AME validate the same at run time.