sumif with left function

Hi,

I'm having trouble getting a sumif to work with the use of a left function.

Here is the formula I have so far (that doesn't work)...

Formula:

=sumif(left(A10:A23,10),A1,B10:B23)

The figure in cell A1 is 10 digits but the range it needs to look at could have 11 or more characters...so it just needs to say "if the first 10 characters match in range A10:A23...sum it..."

Thanks!

Adam