Looking for a simple way to generate one type of spur gear in different sizes

hello,

i have been using the Rhino 'gears' script for a while to generate my spur gears but i would really like to be able to generate them in GH. I have looked at many sites on how to calculate the dimensions of gears and also found a really complicated script (http://www.thingiverse.com/thing:71799/#files) but i am still not much further than when i started.

The basic thing i want to do is pretty simple: i need different sized gears with with Module  0.8 (metric)

SO all i really want to do is select the radius of the outer diameter of the gear size i would like and then have GH generate the number of teeth in the right dimensions for me :)

I have scrapped all my previous efforts which weren't leading me anywhere and decided to start from scratch and ask for help here. I am really not very good in math and geometry and am totally confused by the different terminologies, measures and formulas i found while researching this topic.

Here is my very simple startfile, i hope it illustrates what i want to do .. obviously all the essential parts are missing.

i don't need/want this to become a universal gear type generator (although a 'spur gear' component would sure be usefull i think), i only need module 0.8 gears in different sizes (between 3cm an 10cm diameter).

thanks in advance for any help with this