Try this formula:-

=LEFT(A1,7)&"-"&MID(A1,8,LEN(A1)-12)&"-"&RIGHT(A1,5)

Assumes your data starts in A1. Then copy down.

"bdwood" wrote:

> We start with a cell(s) containing 13 to 15 characters, with no spaces:
> 1234567100AAAAA, 123456710AAAAA, 12345671AAAAA. We want the format to be
> 1234567-100-AAAAA, 1234567-10-AAAAA, 1234567-1-AAAAA. The first 7 characters
> always belong together, and the last 5 characters always belong together. It
> is the middle 1 -3 that varies. How can this be done? Thank you.