I have a created a calculator for technicians and sales staff that allows them to select products, units of measure etc. then add the customer requirements. The calculation takes the input data and calculates units required to meet the request. It also returns the actual numbers based on the product requested.
I would like to be able to type the calculation information into a field in the Item table that is used in the Global calculation field for the output table.
This would let me add products without having to edit the Calculation field ever time I add a new product.
I'm not entirely clear on what you are doing, but consider this:
fieldMyCalc (global, text)
now (by script, button, whatever)
If it's complex:
(2+3) * (6/2)
it can still be evaluated, but you see how you must be careful with the order of evaluation!