I'm an IT Director and I'm working on a spreadsheet that will randomize
employee numbers (1 through 29) so that I can do truly random audits.

Basically, I'm going to hit F9 three times per month to generate
employee numbers to audit and then I'll enter those results in a "Done"
column listed for each month (J16 through J27) and I want those excluded
from future random results.

Any help would be greatly appreaciated.

It sounds like you need to go through the employee list in random order without duplication.

If that’s the objective, I’d suggest a different approach. Make a randomly sorted list once-and-for-all at the outset. Then freeze the list and take the numbers one by one, each time an audit is scheduled.

Here’s one way to make the list.

First, put the employee numbers in A1:A29.

Then put
=RAND()
in B1 and copy down to B29.

Then select columns A:B and sort by column B.

Then delete column B -- it served its purpose.

Remaining in column A is the employee list in random order. You can check off the numbers as they are used to keep track of which was chosen when.

After a list is used up, start over to get a new list randomized differently.

Hope this helps getting started.