Lookup of an Item across markets to fulfil orders

Fellow Excel Users:

I am in need of some assistance! I have a list of "available materials" and I offered to various markets. I have gotten responses, so I would like to map the requested materials on the "Master" tab (green columns) from each requesting market to the "Source" tab of the market (s) that have sufficient quantities to fill the order for the item.

I thought if I used a combination of index/match and if statements would work, but I kept getting errors. In cell F2 on the "Master" tab, I put this formula

=if(index(Source!B:AB,(match(Master!A2,Source!A:A,"0"),if(Source!2:2Source!B:AB>=Master!E2,Source!B4:AB4,"")

To be clearer - for example, in Column "E" on the "Master Tab", I have quantities that that particular market are requesting for that line item. I want to see where that quantity can be found on the "Source" tab and which column on the "Source" tab has the quantity available. If so, give me the location - i.e. A07, A08, etc.