counting cells with data without counting duplicates

I have downloaded data from my accounting package that shows a list of customers and all the part numbers that they have bought this year. I need to find out for each part number how many customers have purchased it. I can do this with a pivot table but it includes the same customer multiple times when they have purchased the same part # more than once, so the count is not accurate.

Thank you in advance for any and all help with this.

Yes! Thank you. That worked perfectly!