Keep CDialog in 16:9 Format?

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Hi,
i need Help again with my Problem.
I have a Dialog with a Browser Control and load a Site with a Video, as the Title says, is there any Way to keep a Dialog in the
Format of 16:9 Format, in eg. if someone change the Width or Height of a Dialog, the Height/Width should be changed to?
To keep this Format permanent?

My first try was in a OnSizing(UINT fwSide, LPRECT pRect) Function but this is not the best way, because any Time i want to resize my Dialog it flickers terribly and i know i make it in a wrong way.
So if someone can help?
Thanks in advance

[GCDEF]

OnSizing seems like the right place. Perhaps you could call SetRedraw(FALSE) on the browser control to prevent flickering.

[VladimirF]

OnSizing is more like notification: there is no way to prevent that sizing.
I would use WM_WINDOWPOSCHANGING message and modify WINDOWPOS structure to maintain aspect ratio.

[Arjay]

Look at the deferwindowpos functions.