Returns the closest point (in WCS) on a curve after projecting the curve onto a plane
(vlax-curve-getClosestPointToProjection curve-obj givenPnt normal[extend])
vlax-curve-getClosestPointToProjection projects the curve onto the plane defined by the givenPnt and normal, and then calculates the nearest point on that projected curve to givenPnt. The resulting point is then projected back onto the original curve, and vlax-curve-getClosestPointToProjection returns that projected point.
A 3D point list representing a point on the curve, if successful; otherwise nil.