Update a bar on screen
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 Syntax

        GT_BarUpdate( nCurrent , nTotal , nTop , nLeft )

 Arguments:

      nCurrent - Current value to be displayed
      nTotal   - Maximum value that can be displayed
      nTop     - Bar row
      nLeft    - Left column of bar

 Returns:

      NIL

 Description:

      Updates a bar at the given coordinates.  The length of the bar is
      given by :

          nCurrent / nTotal * 40

 Examples:



 Header File: GT_LIB.CH

 Source: BARUPDAT.PRG

 Author:  Martin Colloby