I have an array of raw data that spans 15 columns and 4000 rows. In column 1
there is a part number and in colum 12 there is a customer name. These part
numbers overlap to customers fairly often (up to 20 customers for a part
number). How would I, on a separate sheet, return all the customers who use
this part number?

This is what I am looking to do:

Part Number Customer
1 A
2 A
1 B
3 B
4 B
5 B
1 C
2 C
3 C
1 D
4 E

On a separate sheet how do I return the following, without having to sort
the raw data:
P/N Customer(s)
1 A, B, C, D
2 A, C
3 B
4 B, E
5 B, C

Thanks for the help