let’s say that I make a box, then I want to project whatever thing I’m drawing in one face of the box, but while I’m drawing it, and not after that I finished the drawing, as if I was using the project box under the snap settings
I’m assuming you are drawing a curve - start the Curve command and then hover over the Osnap panel. Hit the Ctrl key. The snaps will change into a number of one-shot and persistent options - select the POnSrf option. You will then be asked for a surface to constrain the mouse picks to.
-wim