It would be awesome if the number fields could accept and evaluate basic math expressions, like addition, subtraction, multiplication and division. Parenthesis, etc. It wouldn’t need much to be REALLY useful.
I assume you already know about formula fields and what you are asking is being able to enter a mathematical expression in the number field and have it evaluated into a number to be stored into the field, sort of like what happens in an spreadsheet cell.
I think this is a really interesting idea. For text input, I think a pattern like a spreadsheet that starts with “=” might be the most intuitive. I was also thinking that a simple calculator widget that pops-up might also be a way of doing the calculations (seeing the results as you go) and then storing the final value. This method might eliminate/reduce invalid inputs.
The next question is if the expression is going to be retained. I think there is some value to seeing how the number was arrived at but I imagine that would be a level of complexity that fibery would not support.