It is a row number. When I selected the entire sheet by clicking on the square
above the "1" and left of the "A", Excel put in the "D10_Sheet!1:65536".

tcek wrote:
what is the "65536" stand for in the statement?

"Glenn" wrote:

=INDEX(D10_Sheet!1:65536,MATCH(C12,D10_Sheet!A:A,0 ),MATCH(C10,D10_Sheet!1:1,0))