Need to populate a new field with data from another without having to edit the record

I don't know that I have this set up the best way. I'm just guessing.

I had to create a summary report in a second table (Product List) to get the data we wanted the way we wanted it. Now I need to compare the data. To do that I brought the summarized data from the second table over to the first table (OOS Data). QB won't let me use them in a formula, I'm guessing because they are numeric lookup fields. So I created the form rules to write the data to a text field. Then I used the text fields for my formula.