How to make the current viewport GetFocus and scene pane LostFocus

Heya,

I wrote script to switch the cameras by pressing shortcut key - Shift + Arrows (Up/Down). However, while pressing the shortcut to have camera switched, if the scene pane is focused or a node is selected, there'll be a multiple nodes selection at the same time. Such a 'side effect' is annyoing~

So I wanna make the scene pane LostFocus and current viewport GetFocus before or after the camera switches. How to do that?

Thanks in advance~