simple way to create splines/path at run time?

I want my game to have a character movement system where the user drags a path out away from the character, then the character follows it. What would be a good way to go about doing this. Is there a simple spline system that can update itself at runtime?

I’m beginner so any examples or suggestion are very appreciated.

Well, this is blatant self-promotion, but it does answer the question, so: Vectrosity. It has spline (and spline-following) features, and comes with a line-drawing example.