I don't have very good ABAP skills, so I ask: the changes in the code you did there, do they replace the posting from the customer subledger to the vendor subledger? Or you could do anyway postings to the customer subledger the standard way, provided the account determination is set u...
Then in cash flow, choose the flow and click the button edit flow and choose reverse. This is available in the top of the cash flow tab. Now flows posted on that date will alone be reversed and now you can change the end date and post the correct flows in TBB1 for the last activit...