I have some trouble making calculations on a form using inputs from a table, specifically calculating machine efficiency.



The machine data is input to a form including Running time and Product code, this is all saved to an Orders table. The Product code in the Orders table is joined to the Product code in a Product table which also includes target Production rate.

I want the form to calculate the machine efficiency with a basic calculation, dividing the actual output by the target output ([target Production rate] * [Running time]).

I set up a one-to-many relationship between Product table and Orders table by linking the Product code. But I have trouble getting the form to recognize the field from the Product table.

If I build the form using Form Wizard, I can get it to work, however the pre-existing form has a lot of extra functionality so I'm trying to modify the existing form. I guess it might have something to do with the Source Code but I'm not really sure...

Any suggestions?