Purchase Requisition: Issue with Internal Order budget

Hi,

Requirement is to generate a Error message when Purchase Requisition amount exceeds the Internal Order budgeted amount. I defined availability control for budget profile and i activated the same.& activating availability check (also provide tolerance) for the order type But i am not able to generate the required message.

Commitment management is not active in our controlling area and as well as in internal order master data.

So please suggest how to achieve this in either in standard or custom ?

Message was edited by: Jürgen L Subject changed to the matter