Project Vector On To Plane with using plane base?

There is this blueprint node but it does not do what I need because I also need to define the plane base for it: Project Vector on to Plane | Unreal Engine Documentation

Basically I want to do a trace without doing a trace and just calculating it with math. I know the following:
Start of trace, Plane location, Plane normal, Direction of trace, (Offset for trace)
I do not know the trace length which is the problem. Plane is the hit actor or hit surface if it would be a actual trace.

This is then basically projecting my mouse cursor dragging on to a plane (with perspective), The “offset for trace” is the mouse XY after start of dragging. The “direction of trace” is the direction from camera to start of dragging hit world location.