Restrict edition to horizontal


I'm trying to block the user to horizontal edition only - on grid. I've an object subclassing GoRectangle, and I've overriden ComputeResize to align the size on grid - it works.
I try to do the same with the ComputeMove, but apparently, this method is only called at the start of moving and at the end. So the user can move its object on the grid (snap is set) horizontally and vertically. When he drop his object, it is then aligned on horizontal.
Anyway to block the object to move only horizontaly in the doc ?
public override PointF ComputeMove(PointF origLoc, PointF newLoc) {
return (new PointF(newLoc.X, origLoc.Y));

Is GoView.DragsRealtime true?

oups, no.

I set it to true, and it now works perfectly.
Thank you very much.