Class TButton  --  Introduction
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 TButton()                    Object, not inicialized, constructor
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 Exported Instance Variables

 Row, Col                     Button screen coordinates           Assignable
 Name                         Button Label                        Assignable
 PreBlock, PostBlock, Action  CodeBlocks for WHEN, VALID, ACTION  Assignable
 Pressed                      TRUE when button is pressed         Assignable
 ColorSpec                    Normal & hotkey colors              Assignable
 Cargo                        If you need it, here you have it!   Assignable
 Reader                       Works like GET's reader             Assignable
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 Exported Methods

 New( nRow, nCol, cPrompt, bAction, bWhen, bValid, cColorSpec )   CONSTRUCTOR
 Display()                    Display the Button
 SetFocus( lOnOff )           Changes the button focus
 BtnReader( oBtn )            It is called from within Reader Block