EXIT_SAPLV56U_001 question

Hi,

I am using exit EXIT_SAPLV56U_001 in VT02N to do some additional validation after the shipment has been saved. My problem is that whenever a change is made the exit is not invoked. However, if I do a save without making a change the exit is reached.

I am new to shipments, and am wondering if there is something else I should be doing with this exit, or should I use a different exit altogether.

Thanks,

Roy