I have to fix some problems and enchance form designer written long ago for a database project. In Design Panel class code I encountered these lines

private void DesignPanel_MouseDown(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left)
    {
    	(sender as Control).Capture = false;
    	switch (FMousePosition)
    	{
    	case MousePosition.mpNone: 
    		SendMessage((sender as Control).Handle, WM_SYSCOMMAND, 0xF009, 0);
    		break;// Move
    	case MousePosition.mpRightBottom: 
    		SendMessage((sender as Control).Handle, WM_SYSCOMMAND, 0xF008, 0);
    		break;//RB
    	case MousePosition.mpLeftBottom: 
    		SendMessage((sender as Control).Handle, WM_SYSCOMMAND, 0xF007, 0); 
            // ... here are similar cases ...
    	case MousePosition.mpLeft:
    		SendMessage((sender as Control).Handle, WM_SYSCOMMAND, 0xF001, 0);
    		break;//L  
    	}
    }
}

FMousePosition indicates whether mouse was over any edge of selected control.

What confusing me is these windows messages: it seems there is no documentation on WM_SYSCOMMAND with parameters 0xF001-0xF009 (maybe it starts some kind of 'drag/resize sequence'). Any ideas?

If my suggestion is right, then how can I cancel these sequences?