Easy modification for sprocket?

Here's my dilema and I'm not seeing an easy solution and I'm a newb to formulas, there's already a sprocket file I  rountinely use but I need a sprocket to have 80-90 teeth the one file I have now is 20tis there a formula I can do on this design (attatched below) to make the diameter bigger as I chain the number of teeth?

SolidworksGeneral