*snip*
>Don't think so. Drop a treeview on a form. The treeview is a child window. However, it does not respect LockScreen = .T. The only way to specifically lock the update is to call LockWindowUpdate() with the window handle of the treeview itself.
>

From a few tests, it appears that VFP does not issue a LockWindowUpdate at all and that is why the child window doesn't respect it. I set LockScreen = .T. on a form. I then used Foxtools.Fll to get a window handle on that form. I issued LockWindowUpdate myself manually and was able to do it.

It also explains why you can have individual LockScreen properties on each form and they work. If it did issue a LockWindowUpdate, you couldn't do that.