Good plan. I have a Master Table "Printers" and a child table "Print Jobs". Each Print Job is assigned to a printer and does a lookup to find the speed of that printer from the printer table. I then want to edit this printer speed depending on the criteria of the print job, each of which is a different field (1-sided vs 2-sided, black vs colour etc) to give us a more accurate speed for the printer for that job. Also how much this speed is adjusted will depend on the printer assigned (printer 2 might take twice as long for colour whereas printer 1 might only take 1.5x as long etc).