If you want to simply count the number of entries in the range, you can use a
formula like:
=counta(a1:a10)
(where A1:A10 contain your data)
If you wanted to count the number of unique entries in that range, you could use
a formula like:
=sumproduct((a1:a10<>"")/countif(a1:a10,a1:a10&""))
(you can only use the entire column in xl2007)