A FieldMaps Form Builder element that computes an entry akin to an Excel function

[Christman]

Form elements come in different input types. I am proposing a basic form element that allows the user to input a mathematical expression to be calculated. Just like a cell entry in Excel can evaluate a function that include numbers and variables (i.e cell C4 =B4^2*3.14) but the displayed value of C4 is the evaluated expression (if  B4=2  then C4 = 12.56). 

In a FieldMaps example, the Smart Form 'basic element' would allow the user to select a single entry box in their Smart Form, type an expression of numbers and other variables, and return a single value to that field.

So  "(4x5) + (6*7/2) + (5^2) - fail" entered into the field returns "50" if 'fail' = 16.

I am inspecting recently constructed sidewalk/ADA ramp improvements. Different parts of the improvements are paid for by area and are bid out separately so individual sidewalk panels must be measured and associated with a specific bit item. However, area measurements first require a length and width measurement. I have to make a lot of measurements so being able to enter the measurements directly into a field associated with a bid item and have them be calculated directly would really allow me to move quickly and record area measurements efficiently. 

Maybe there's an easier way to incorporate some kind of simple calculator into these SmartForms but I am open to suggestions and comments.