check deliveries when inserted in shipment

Hello people,

could you please give me an advice how to solve my problem? When I create shipment in VT01N, fill header data, I want to insert deliveries. So I press button "Deliveries", set proper data and press "Excecute" button. At this moment I would like to enter list of selected deliveries and do some ABAP code to check deeper deliveries's relevance for shipment.

I found some userexits V56* which can be maintained via CMOD, but they work only when save icon is pressed - too late for me - I do not want to adopt deliveries, which don't pass through my ABAP code.

Thanks for your help.

David