This is a basic sample of what I have in Colums A and B:

123 a
123 b
654 d
654 a
654 r
789 b
789 q
963 s

This is the format I would want two news columns in:

123 a,b
654 d,a,r
789 b,q
963 s

Basically I am trying to merge all the identical A cells while combining the adjacent data into a single, new cell. There are thousands of these, but this is the basic idea.

Any thoughts. Thanks.