I"m working on an inventory sheet which constantly changes in size.
If there is a way to do this with Functions, i would rather that because
this is a report that is run over night when i'm not here. If not, i guess
we can find a way.

I'd like to look down column A and look at every single item.
If there is no duplicate, do nothing
If there are duplicates, it should first find where A and B = each other for
that particular #. Then take all the cooresponding #'s in B and concatenate
them in Column C (each seperated by a colon) on the row where A and B were =.
see below for a visual.

examples
A1 = 364691-001 B1 = 364691-001 C1 = 364692-001:364695-001
A2 = 364691-001 B2 = 364692-001 C2 = (empty cell)
A3 = 364691-001 B3 = 364695-001 C3 = (empty cell)
A4 = A3509A B4 = A3509A C4 = (empty cell)

A1,A2,A3 are duplicates
A1 and B1 are equal to eachother
Take B2 and B3 and concatenate in C1.
C2 and C3 can stay empty
A4 and B4 = eachother, but there are no duplicates so C4 stays empty


I"m not sure if indexing, Vlookup, if, then, next and loop will be needed or
not.
I'm open to any suggestions.