I'm trying to figure what function I need to use. I unerstand that when
order does matter I should use Permutations and Combinations when it
doesn't. For example if I want to know how many two letter group I can make
from the word CAT and order does not matter I'd use Combinations and the
results would be CA, CT and AT. But here's my question, what if I needed to
know how many different Combinations I could have from three blank spots to
all letters. On something small I like CAT I can just write them out.

CAT
CA_
CT_
AT_
C_ _
A_ _
T_ _
_ _ _

COMBIN does't work. The first number I'd enter for the formula would be the
total number of letters, in this case 3. The next number is the number of
groups and this is what seems to be the issue. I got the right answer when I
did =COMBIN(3,3)+COMBIN(3,2)+COMBIM(3,1)+COMBIN(3,0), but what do I do if I
have 15 letters. The must be a function that does this that I'm not
finding??

Thanks,
Mark