Hello my friends. I am really interested to learn how to communicate with solidworks using other application?

All what I need is to startup solidworks and modify parameters of somesimple models (example diameter of extruded cilinder) but new parameters will be sent from my application.

I heard somewere that this could be done using some "dll"  or something like that.

Please, If someone could explain me how it works I will be greatfull.

Thanks in advance.

Danijel