MdiChildren Collection and ChildActivation

Hi !
I'm looking to a strange problem.
I have an MDI form and this has children. when I look to the order of that children in the MdiChildren's collection this seems to be always the same. I'm using my Dockable Windows and all works fine, but when I'm closing one of this dockable windows then The MDI form gets informed about that In a way I cannot find out,( Control removed seems to be fired by the MDI Fom) how this is done. The result is the order of the active Forms on the screen sometimes chages, sometimes not. It seems to activate that child, which was created first in my MDI as the new top window, independen which Form really was the last active on screen. Anyone knows what could activate an event in the MDI itself so it changes the order of the forms in MdiChildren? ( this seems to be the reason for the activation change )
--------
Now I have written a method to re-arange the forms in the ControlRemoved event delegate of the MDI Form so I get the correct form on top again, but I cannot reorder them in the same way they had been before closing.
Is there a way to read out the Z order in which they had been before closing my DockingPanel ?