REDRAW   GuiFile 

This command will Re-Draw the GuiFile's window, taking into account
any changes you may have made to the GUI with the ChangeGad command
or with the SetGad command (with the SHOW|HIDE keywords).

Use it after using ChangeGad or SetGad on all the gadgets you want
to change.

example :

   setgad mygui.gc 1 HIDE
   setgad mygui.gc 2 SHOW
   redraw mygui.gc

A cooler redrawing can be achieved with the  PartRedraw  command.