If there are a lot of spaces or commas, then this might work. It just
checks to see if the first 10 characters has a space or a comma and
returns false to indicate that line doesn't have an account number.
If there are other common characters, then you could also search for
those, but to search for any non-number would be a little more complex
and likely require a custom function.

=AND(ISERROR(FIND(" ",LEFT(A20,10))),ISERROR(FIND(",",LEFT(A20,10) )))