=IF(D1<10,B1,C1)
but I don't think that is telling you much.
The difference is if you put that formula in A1, and then copy it to A2, A2
will then be
=IF(D2<10,B2,C2)
whereas if you start with
=IF($D$1<10,$B$1,$C$1)
copying it down to A2 will result in the same formula in A2 as in A1.
--
HTH
Bob Phillips
(replace somewhere in email address with gmail if mailing direct)