Alert before adding Document

Hi Expert,

I need to get an alert while trying to Add/Save a PO if "the existing quantity of the item in warehouse + the quatity specified in purchase order is greater than the maximum quantity". I need the alert to be fired before the I add the documet so that the user can decide whether or not to continue with the documnet.

I have searched the forum and havent seen any links for this.

Is there any method for doing so or any work around with which I can achieve the similar effect.

I'm using B1 2007 B.

Please Advise

Thanks & Regards

Jaics