Oh, I think I understand.
Ideally, you need something like

• find the nearest edge of the path
• go to this edge
• stop when you are in front of the mouse click

So far we don't have a function to get the nearest edge, you have to develop something approaching, for example :

• find the nearest node of the path
• explore all the edges of this node
• mesure angle between mouse click and edge
• use edge with the smallest angle
• follow this edge and stop at the minimum distance of mouse click

Might be a good function to add in the DLL...