Query calculations with key fields

[tscotti]

Hi,

I'm having trouble calculating query results using tables and their primary key fields.

For example, the primary key fields of my linked tables are "ProductID", "Description", and "Colour".

In my inventory calculating query, I want the sales amount of item "001" "Widget" "Black" to be subtracted from the opening inventory amount of "001" "Widget" "Black".

The problem is that my query is also subtracting the sales amount from the opening inventory of "001" "Widget" "Red" !

I hope that I've explained myself well.

Please help!

Thanks,

Tony