Hi Bob ,
The main point is how many random numbers do you want to generate ?
If it is only a few , then the simplest way is to generate random numbers between a much larger between-set , say between 1000 and 1000000 , and then select only a few numbers from these randomly generated numbers ; the chances are bright that all your numbers will be unique.
If you are going to generate 70 or more numbers between 15 and 100 ( whose difference is only 86 ) , then randomness does not mean much , since almost all the numbers will be present , only in random order.
Try this out :
1. In any column , say column D , fill in the numbers from 15 to 100 ; they will be in sequence.
2. In the next column , which will be column E , enter the formula =RANDBETWEEN(15,100) , in the 86 cells corresponding to the cells which have numbers in column D. So if your original filled-in numbers are from D7 to D92 , the formulae should be between cells E7 and E92.
3. Sort both the columns on column E ; your numbers in column D are in random order.
Narayan