urgent

Hi sap guru's

I have a doubt am stuck in a implimentation on ATP where they want reservations i will explain you all with example

Cust A

Cust B

Cust A ordered 10 qty and cust B ordered 10 qty for cust A i got a delivery date of 07/22/07 for eg and for cust b i got 07/23/07 and i decided to deliver the goods first to Cust b and hold cust A for more time so my question is whn i deliver to cust b there will be an ATP check again on delivery level so whoz stock it gonna conform Cust A stock or Cust b Stock as i hve only 10 stock available in my hand my client req is they dont want cust A stock to get disturbed

2) they have internation customers too where they do partial delivery to them if for some reason theydont deliver 1 item and they want to delive it with next shipment is it possible

so please kindly give me step to step configuration steps

Thanks in

advance