Creating a comma seperated list based on a search criteria from a column

Hello everyone.

I have spent the last 2 days trying to find out how to do this, but I am not getting anywhere. I am not great with excel but can usually find a work around for things, but this time I am stumped.

I have to create from a list of child SKU'S in a cell, comma seperated that relate to the parent items in a file I have to create (there are over 2000 parent items, totally around 44000 skus when you include the child items, so manually is out of the question).

The idea being, that when I import the parent item product, in one cell there is a list of the child items for that product. Hopefully the image below helps explain.

Attachment 274052

Thanks in advance for any help.

Steve

as requested