I want to create versions of the edit tools that will add a parallel, offset segment each time I add a segment regularly. Is it possible to put a wrapper around the existing tools? Or otherwise add to their functionality?

e.g. Using the sketch tool I click twice on the screen. Code that I write would add a perpendicular segment on the front of a specified length and a parallel segment. I add another segment and it adds another parallel segment. I add a curve and it adds a parallel curve.

Do I have to make the tools from scratch or can I use the existing ones to add the segments and just tack on code to add the extra segments? Recreating the sketch tool wouldn't be so bad but the other tools are more complicated.