Inefficient code: Prevent generation of duplicate random numbers

I have some code from a larger program. This part generate random numbers within a range and checks for duplicates. I have placed print statement to help with getting a handle on scope. If a duplicate is detected I want a new random number to be generated. The code works but I think an experience programmer would laugh at how ineptly it does it. So I was hoping for some guidance on how to improve this code.

Code Extract