I don't think this problem is too complex but the logic's confusing me at the moment and a few heads might be better than one.

In column A I have a list of document filenames which relate to the product they represent. These come from a number of different sources, which are listed in column B. So if I've taken a document for product X from source Y, column A will contain an X and B a Y for that row.

Some of these product names are duplicated, so I've created a macro which trims the list in A into a list of unique product names in column C. Some of these are duplicated because there is a similar document from multiple sources but I'm interested in the ones which are duplicated in the same source.

So I'm looking at the unique product in column C, looking back to the original data in column A which may have multiple references to that unique product. Then I want to look across from those cells at column B and check if the values in there are the same. If they are then I want to put an indicator in a new column relating to each source.

Currently I'm trying to code something in VBA (I'd be open to a spreadsheet solution) and can lookup and find references to the corresponding cells in A but I'm unsure how I can compare the values in these references as I'm struggling to find them simultaneously.