exchanger option? exchange x amount

[Tassadar 8]

Hello, I was wondering if there is a way to increase amounts purchasable from an exchanger npc?   instead of dragging 1x item to the purchase bar, I want players to have the option to exchange X amounts. Is this possible? If so, how would I implement it?

[Snre3n 94]

If you use source, I would start looking at these two functions:
CNpcTradeMgr::LocalBuyFromNpc
CBlackTradeMgr::SailToBuy