select: additional to the visible label, a hidden value for computation is selected
radio: selects a hidden value for computation
number: presents value to compute
compute contains an arithmetic expression consisting of constants and references to computational selects, radios and/or number fields and displays the result of the computation.
My idea:
Extend existing field types:
compute contains an arithmetic expression consisting of constants and references to computational selects, radios and/or number fields and displays the result of the computation.