Using POI only as a formula evaluator

Hi,

I am currently working with forms for surveys and I want to implement a
simple possibility to make the users to add formulas for calculation of
scores and relevance (to show ore hide) of questions.

I thought: Why should I implement my own calculation language when I can
use a language every user may already know?

So I came to the idea to use POI. I thought of parsing throw a formula
and replacing variables within that formula with values - and then
letting POI evaluate it.

Is this feasible? Is it possible to only evaluate a formula without
creating a temporary spreadsheet?

Where in the javadoc of POI should I begin? Or does someone already has
an example?

Thank you,
Philipp