If there's only one instance then perhaps:

A1: =LOOKUP(2,1/(($C1=$E$1:$E$100)*($D1=$F$1:$F$100)),$B$1:$B$100)

IS that what you mean ?

Better to post a sample file I suspect... what are the values in B - numbers ?

Do you have duplicate matches and if so what do you want to do with the duplicates ?