Unless you're talking about the criteria portion of
SUMIF, you can't. But you can do this:

=SUMPRODUCT((LEFT(A2:A100,3)="jas")*B2:B100)

Which calculates as:

"Sum everything in col. B where the first 3 characters of
the values in col. A = "jas".

HTH
Jason
Atlanta, GA

-----Original Message-----
For example:

Left(a2,3)
within a sumif function

How to do that?
.