twMakeShadowArea( sT, sL, sB, sR, wSType )
 ----------------------------------------------------------------------------
     Display a shadow around a region whose underlying screen region is
     defined by the coordinates. This function creates the shadow in
     accordance with tye value of Shadow Thickness set by twInit().

       Arguments:

     sT,sL
     sB,sR   - 'N' The coordinates of the underlying screen area around
                   which the shadow is to be placed.

     wSType   - 'N' Shadow position based on the numeric keypad method
                   described earlier.

       Return:

     Current Window Handle.

       Example:

     twMakeShadowArea( sT, sL, sB, sR, tShadow )