Eliminating flicker when using a custom resize function

I'm using a custom resize function so that the dialog I'm using automatically resizes the controls on it to keep certain distances between the controls
(Yes the controls grow if the dialog grows & shrink if the dialog shrinks)
The only problem so far it that the dialog flickers when ever you start to resize and move the mouse while resizing.

stopping the updating of the window won't help in the OnResize function

I have tried to stop updating when the mouse button goes down (OnLButtonDown)
but it looks like that function is never called when you hit the side of the dialog.

An OnIdle functions to update if the updating is turned of doesn't work either
never accessed in the dialog for some reason.

What do I need to do to get a flicker free resize option ?