You are behaving like a troll. To say as you do:
makes me wonder if you even understand what random numbers are. And, yes, I studied statistics at Uni. Have you ever been in one?

Your assertion that one has to:
suggests you only know of the crudest brute-force methods of approach to such problems.

For a solution without repeated numbers, simply add another column, B, with:
B1 =COUNT(A$1:A1)
Copy B1 down to B75
B76 =SUM(B1:B75)
Then, with the macro, change:
While Range("A75").Text = "#NUM!"
to:
While Range("A75").Text = "#NUM!" Or Range("A75").Text < 80 Or Range("A75").Text > 600 Or Range("B76").Value > 75
Just be prepared to wait a long time while Excel does the recalculations. There are, of course, other methods, such as using:
While Range("A75").Text = "#NUM!" Or Range("A75").Text < 80 Or Range("A75").Text > 600
then, when Excel calculates a series with duplicates, change just the duplicates... but I guess the thought never occurred to you that might be possible.

End of story. No "calculate the more then 33681*10^90 combination" required. The fact you don't know how to do this doesn't mean it can't be done - and quite simply - if you know what you're doing.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]