There is an API to display dialog in center of the screen i.e. CenterWindow() but
I don't know if there is direct API to display it at bottom right corner.
My suggestion is first calculate the screen coordinates
void GetScreenSizeInPixels( SIZE& s)
ZeroMemory( &s, sizeof(SIZE) );
s.cx = (LONG)::GetSystemMetrics( SM_CXMAXTRACK );
s.cy = (LONG)::GetSystemMetrics( SM_CYMAXTRACK );
Than calculate the Dialog size using GetClientRect and than calculate the position and now use SetWindowPos with property SWP_NOSIZE.
May be this will help you.