twMPause( nSeconds, nStart )
 ----------------------------------------------------------------------------
     Wait for a given period of time. This function operates according
     to the speed of the machine

       Arguments:

     nSeconds - 'N' Input the number of seconds to wait.

     nStart   - 'N' Optional time in seconds ( SECONDS()) from which
                    the nSeconds seconds are to elapse.  You may set a
                    time between the start of events which could take a
                    varying times.

       Return:

     NIL

       Example:

     twMPause( 5, SECONDS())