I am attempting to make unique user Id's using excel or access.
I want to CONCATENATE a first name and last name into first initial
last name but if there are duplicates I want the second one to be
first initial last name 1.

ie: john doe jdoe
joe doe jdoe1

Off-topic a bit, but hopefully you've thought ahead about what will happen
in the future when new people arrive or current people depart. If the first
"john doe" departs, for example. Most likely, you'll want still-in-use
id's to stay the same.