Help!! Can't work out after two days trying - Unique Count with multiple Criteria

Hi All Excel Experts,
I have tried my best, Googled, etc and after 2 days (10+ hours) I have admitted defeat and come to you for help.

I have two separate columns that I need to use as criteria
eg Sales Rep = WA
Item = 1021

Using these two criteria I want to be able to count the number of customers you have met this criteria. Some of the customers will have met this criteria more than once, but I only want to count them once (trying to work out how many customer have met the criteria).

I need to be able to do it in a formula as the data will ultimately be from an External Data source, hence I dont want to use a "Remove Duplicates"

More details in the Test Data

Many many thanks in advance.

Cheers Andrew

Hi bebo021999,
Thanks so much for your help!!!

My mistake re: "1) ID 023017& 023018 for same customer "YOR". Not test for other ID. Try it!" I accidentally changed the ID number

I see the problem with String Text V's Number. Great point!

Your formula works perfectly. I will now study it so I can learn from it.

Thanks again for your help. I was defeated. Have a great day : )