VBA =RANDBETWEEN

I hope you can help me figure out what I am unable to do myself. I work as an Auditor with large data sets and want to make taking samples easier for myself and everyone I work with.

I am trying to set up a random number generator using =RANDBETWEEN

What I would like to do is specify a field in which I type the range i.e. (1,20) and then for =RANDBETWEEN to pick that value up and generate numbers, but WITHOUT repeating any.

I bet there is a way, I just haven't considered it most likely and have a blonde moment.

Any help would be really appreciated.

Thanks