R_Ntx() 
 Indexes a DBF file, displaying a progress bar
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 Syntax
        R_Ntx ( cIndExp, cFileName [, cHeader [, lUnique ] ] )

 Arguments
        cIndExp         Index expression

        cFileName       Name of the index file (default extension is .NTX)

        cHeader         Header text for bar
                        Default text is : "INDEXING: <Alias>"

        lUnique         .F. : create a non-unique index (=default)
                        .T. : create a unique index

 Returns
        NIL

 Description
        (Re-)Indexes a DBF file, displaying a progress bar.
        The function is similar to the dbCreateIndex () function.

        +----------------------------------------------------------------+
        |                         -+- CAUTION -+-                        |
        |                                                                |
        |     IN THE UN-REGISTERED  VERSION OF RBARLIB THE FOLLOWING     |
        |     REGISTRATION MESSAGE WILL BE DISPLAYED AT RANDOM TIMES     |
        |     (WHILE EXECUTING THE R_NTX() FUNCTION) :                   |
        |                                                                |
        |     Unregistered version of RBarLib - Wait for 8 seconds.      |
        |                                                                |
        |       AFTER A 8 SECONDS DELAY THE PROGRAM WILL CONTINUE.       |
        +----------------------------------------------------------------+

 Example
        *-- Create an index file with the name NAME.NTX

        R_Ntx ( 'Upper(NAME)', 'NAME', 'Just a moment, indexing <PERSONS> ' )

        More examples can be found in the demo program RBarDemo.PRG.