Counting Unique combinations

Can someone, anyone please help. I have a spreadsheet that has 2 columns. The first is a vendor code, and the second is a part #. There are many vendors with multiple part #'s per vendor and duplicates. In other words, (for example sake), a vendor has 20 part numbers associated with a particular vendor #,and there are many duplicates within the list.

I am trying to do a vlookup and count how many items are associated with the vendor. But I have to exclude duplicates and only count the part once? This is very frustrating. Is this even possible? ANY help would be appreciated. Below is an example.....

SHEET 1
Column A (supplier)......................Column B (part#)
xyz corp.......................................12345
xyz corp........................................78910
xyz corp.......................................12345
ABC Corp......................................99999
ABC Corp......................................55555
ABC Corp......................................99999

SHEET 2
Column A (supplier)................Column B(# of parts)
xyz corp.....................................2
ABC Corp...................................2


So based on this, I want to COUNT how many times the part # shows up for xyz, and ABC and then I need it input into another sheet. So the logic verbally would be......lookup xzy in the first sheet, count how many exclusive times the part # shows up for that supplier, and return that count in the new sheet.

I hope that make sense.