PostMessage() across process boundaries equivalent

[TheKedge]

Hello,
is there anything equivalent to the windows PostMessage() across application boundaries?

HWND hWnd = ::FindWindow(NULL, "MyOtherApplication");
::PostMessage(hWnd, IntegerMessageID, 
				(WPARAM)param1, 
				(LPARAM)param2);

HWND hWnd = ::FindWindow(NULL, "MyOtherApplication");
::PostMessage(hWnd, IntegerMessageID, 
				(WPARAM)param1, 
				(LPARAM)param2);

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I've got Qt GUI apps talking to a COM server that sits on a big heap of code. Parts of that code should be able to tell the GUI that it needs updating. Before I started using Qt I was using the PostMessage(). My GUI could catch it and ask the COM server for fresh info.

any (simple) ideas?

thanks
K