Use Data Found In Form To Populate Select Options?

I have a page that runs a lot of calculations.The math is computed on the fly using java scriptwhen all the calcs are in, prior to form submission the user needs to evaluate which numbers they prefer, and from there, once they select them, the form, based on those choices, will perform one last calclets say we have 3 result fields

r1 = 2000
r2 = 3000
r3 = 4000

what i want to do is have a select field be able to display those values at the bottom of the page;for example

<select name="s1">
<option value=[field contents of r1 above]>[field contents of r1 above]</option>
<option value=[field contents of r2 above]>[field contents of r2 above]</option>

[code]....