Use this as an array formula (confirmed by pressing Ctrl+Shift+Enter).

For Excel 2007 and above,
Formula: copy to clipboard
=IFERROR(INDEX(C:C,MATCH(G2&G3,$A:$A&$B:$B,0)),"")
For versions prior to Excel 2007,
Formula: copy to clipboard
=IF(ISERROR(INDEX(C:C,MATCH(G2&G3,$A:$A&$B:$B,0))),"",INDEX(C:C,MATCH(G2&G3,$A:$A&$B:$B,0)))