Ooops, sorry, misread your post and did it backwards:
=INDEX($C$3:$C$6,MATCH(INDEX($A:$A,ROW(B10))&INDEX($9:$9,COLUMN(B10)),$A$3:$A$6&$B$3:$B$6,0))

That's another option without a helper column. It's an array formula so needs confirming with ctrl+shift+enter, drag across/down as neccessary.