I don't think I understand you - do you want to create MB21 reservation from PR? if so why?
Stock: 50 EA
Demand: 150 EA
Shortfall: +50 - 150 = 100 EA
Then MRP runs:
PR created for 100EA
You automatically want to create reservation for 50 EA and change PR qty to 50 EA
Stock: 50 EA
Demand: 200 EA (original 150 + new reservation 50)
Expected receipts: 50 EA
Shortfall: +50 - 200 + 50 = 100 EA
You are back where you started or am I missing something?
