For a single criteria, Vlookup is the way to go. However, with multiple
criteria, I would recommend SumProduct().

=SUMPRODUCT(--($A$2:$A$3="George Oday"),--($B$2:$B$3="10100"),C$2:C$3)
using the double negative (--) before each condition makes it a 1 or 0 for
true/false comparision.. in the current format, it looks at your table (rows
2 and 3) and checks if George Oday is in Column A, and 10100 is in Column B,
from there it sums whatever is in Column C.

SumProduct was confusing the first time I used it, so if you have any
followup questions, I'd be glad to answer them (although I know there is a
lot of answers in these newsgroups already, you might be able to find more
faster answers there!).

Hope this helps, Jim
--
I appreciate any feedback.