Alingned Node Coordinate Value (TCL Script)

Hi,

How can I determine the node coordinates aligned from two nodes without need to use a temporary node technique.

A function type:

Input1:   two nodes N1 and N2    ( For Vector Definition)

Input2:   Node   N3  ( To be projected perpendicularly  to N1 and N2 vector )

output:  Aligned N3     (New Coordinate  ==>  X,Y and Z )

Thanks in Advance,

Felipe