How to calc an area and to show fields on product?

I’ve addes option height and lenght for a single product that need of these info to can calculate the price that’s [(height*lenght)/100]*Price
I’m not able to show the fields on the product so that user can insert and i do not founf how to set the proper formule to can have the price result.
Can you help me?
What can i do to add more of one product with differents measures?
F.E. about windows on home i chose the tye of material and i add differents heights and lenghts for variouses house’s windows.
Thank you