Counting Unique Values in a Named Range using COUNTIF

Currently trying to search for unique client ID #s across a large database with non-contiguous fields. I created a named range to hold all of the client ID fields. Currently playing with these two formulas, but I keep getting a #VALUE! error.

Option 1: =SUMPRODUCT((clientid<>"")/COUNTIF(clientid,clientid&""))

Option 2: =SUMPRODUCT(1/COUNTIF(CLIENT_ID,CLIENT_ID))

The only ideas I've got left get real messy real quick. Anyone know of any straightforward forumlas I can apply to this situation? Let me know. Thanks.