Mauro,
Did you face the same issue on your clients?
No, I have never heard anyone request that they wanted ATP done during GR. My experience is that businesses that commit to a MTS solution do not really concern themselves with priorities other than 'date' during the receipt of goods into stock. Those businesses who do have additional prioritization schemes other than 'date' satisfy those schemes via V_V2; typically using delivery priority or a custom sort. V_V2 is commonly executed on a regular basis, to reorder confirmations to meet business prioritization requirements.
I don't think it would be wise to use your 'custom program' to directly update committed quantities unless you have an indepth understanding of how availability checking really works. What sounds like a very simple solution could end up as a nightmare in detail.
Best Regards,
DB49
