In article ,
Don_Quixote60 wrote:

Afraid it's not that easy.

That's a particularly uninformative response, especially since you gave
no formatting or other info in your post. Can you explain why not?

If you've got ISBN-13 PLUS a check digit, and one or more dashes, then
one way:

=MID(SUBSTITUTE(A1,"-",""),4,10)

And of course, after the 978 prefix is completely assigned, the 979 and
following ISBN-13's CAN'T be converted to ISBN-10, so

=IF(--LEFT(A1,3)=978,MID(SUBSTITUTE(A1,"-",""),4,10),"INVALID")

If you've got something else, try posting more info.