Well, sorry to say it didn't work. I've got this code in the NodeClick of my treeview:

IF node <> This.OldSelectedItem
   DECLARE INTEGER LockWindowUpdate IN WIN32API INTEGER hWnd
   = LockWindowUpdate(This.hWnd)
   This.SelectedItem = This.OldSelectedItem
   = LockWindowUpdate(0)
ENDIF 

When I click on another node, it's moving me back to the old node, but it's not locking the screen while the highlight moves to the new node and then back to the old node again.