windows belonging to different processes are mixed in a single window hierarchy

[xrg_soft 163 com]

From MSDN page for WM_ACTIVATETOPLEVEL http://msdn.microsoft.com/en-us/library/xkd95027(VS.80).aspx[^] I got the below description: This message is similar in use to WM_ACTIVATEAPP, but works in situations where windows belonging to different processes are mixed in a single window hierarchy (common in OLE applications). Does anybody know where is a example/demo available that illustrate "windows belonging to different processes are mixed in a single window hierarchy"? I googled but found almost nothing. Thanks!

[Kyudos]

I would assume that this will happen when (say) Word runs its windows inside your application to deal with an embedded object? So would apply to the windows / processes associated with any OLE object.