Help with random sampling, please.

I'm struggling agian with random sampling. I've got the attached spreadsheet with macro set up to test out in a way that will easily tell me if I'm getting duplicates. I'm getting duplicates! Worse yet, some times I get the Column Header as an output.

Please, Help!

I'm also eventually wanting to set this up so that it checks previous runs for duplicates (back about 3 runs). I figure I'll manually copy each output into a running list that I can have it check against, and only keep outputs on that list for 3 runs or so, but am not sure how to do the macro to check against this list for duplicates.