Returns the internal height of a window (without title bar and border).
//Internal height of the "WIN_EditCustomer" window
ResHeight = WinInHeight(WIN_EditCustomer)
<Result> = WinInHeight([<Window>])
Internal height of the window (in pixels).
<Window>: Optional window name
Name or alias of the window to be used. If this parameter is not specified or if it is an empty string (""), the internal height of the current window is returned.