AX2012: Mark a InventTrans (salesline) up against a InventTrans (purchline)

Hi
I hope that this is the right place to ask this question.
Otherwise, I kindly ask You direct me to an appropriate place.

I need a piece of code that marks a salesLine up against a purchased party (purchLine). I have found several examples solving the problem on AX2009, but I haven't succeeded porting the code to AX2012.

I have by code created the SalesTable, SalesLine and the InventTrans, that vil reserve/draw the items from the stock, and I have found the InventTrans, that comes from the PurchLine. How can I by code mark the quantity of items I want to reserve/draw from that purch-inventtrans?

Best regards Ebbe