Help with "OR" in data validation|General Excel Questions & Answers|Excel Forum|My Online Training Hub

I am running Excel 365. I have two named tables, one is called "Inquiry" and the second is called "JO." This is a customer service type database, where first we get an Inquiry, which we log in the Inquiry table in the column named "Inquiry Number." At some point, a decision is made on what to do with this inquiry. If it goes to the JO group, then the data entry person goes to the JO group and enters the inquiry number into the column named "InquiryNum." Now the project is tracked by this group.

Anyway, in the JO spreadsheet, I want to make sure that there are no duplicates. So I made a data validation statement:
=COUNTIF(INDIRECT("JOLog[InquiryNum]"),INDIRECT("JOLog[@InquiryNum]"))0

This works too!

The problem is, I cannot figure out how to combine them in an "OR" statement. Can you help?