Need to update cells based on the value of another cell

Hi All,

I think the title over simplifies my query somewhat!

I am trying to clean up a spreadsheet passed on to me. Essentially my problem lies in the 2 columns shown in the example file.

Essentially what i want to do in the cell to the right is assign each box its own id. For example for John i will want the value in "boxID" to be "John-a, John-b" for Eric, "Eric-a, Eric-b, Eric-c...etc through to Eric-h"

I have been trying to teach myself VBA but this is a little complex for me to get my head around at my current understanding.

Hope that makes sense and thanks for any help anyone is able to offer!