My apologies...You indicated that the numbers would be constrained between 75 and 90.
Try this regular formula:
=MIN(MAX(CEILING((A1-75)/3,1),1),5)
Does that help?
I'm guessing that what you *meant* to say, originally, is that you want to rank a series of numbers between the minumum and maximum values for that series, right?
Assuming that's correct, put this regular formula in B1 and copy it down as far as you need:
=IF(A1="","",MIN(MAX(CEILING((A1-MIN(A:A))/((MAX(A:A)-MIN(A:A))/5),1),1),5))
Does that help?