I have a bunch of cells with strings like this: (RUP((x+7)*2 +45)*2).
The actual formulas don't matter too much, other than that they aren't
all the same - there are a number of different variables and
parentheses sets.

I'd like to make a function that will allow me to use these strings
mostly as-is. I'm trying to define

RUP(string) = WorksheetFunction.RoundUp(string, 0)

without having to go through and try to replace any text in the
original strings. I'm not sure how to go about this other than
including a lengthy formulation for "string" in the function. Is there
an easier way to do this?