There are formulae which can give you unique values bunched up so there
are no gaps, but you might find it easier to record a macro while you
go through the procedure I gave you - i.e. produce unique values in a
separate sheet using Advanced Filter and then count them. You could
assign a keyboard shortcut to the macro and store it in personal.xls,
so that you could run it again anytime you want to.

Hope this helps.

Pete