Anonymous ID for repeat entries

Bit of an odd title, sorry. I’ve run into a problem at work that I’ve almost solved. I would very much appreciate it if someone could assist me, since I’m spending a lot of time doing this manually right now :).

I’m working with a list of 7 digit numbers, up to 6000 entries, like this:

7462828

9375728

8472782

0938217

Currently I’ve worked out a way to identify repetitions, ‘count’ the repetitions in the next column and assign an unique ID to the first entry of any number that has repetitions somewhere in the list.

7462828 1 ID208

9375728

8472782

7462828 2

0938217 1 ID372

7462828 3

0938217 2

What I can’t figure out is how to automatically add the unique ID I assigned to the 7 digit number, to all following (and newly added) entries of that number like so:

7462828 1 ID208

9375728

8472782

7462828 2 ID208

0938217 1 ID372

7462828 3 ID208

0938217 2 ID372

Working with databases would obviously be a better solution but that’s something we will have to implement at the start of the next project.

Thanks a lot, any solution (macro/formula/vba) is welcome.