50g

How do I store an equation (written in RPN mode, either in the 
equation writer or as text to the stack) to my SD card (or any other 
directory)?  I have a lot of complex fluid, volume, and pressure 
calculations that I would like to just be able to pull up the equation 
and enter the variables to solve.  It would save me some critical time 
if I had the formulas ready to use.