List an array and allow selection.
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 Syntax

        GT_Choose(<aOptions>,[<cTitle>],[<nTop>], ;
            [<nLeft>],[<nBottom>],[<nRight>],[<aValid>], ;
            [<nStartItem>],[<nStartRow>])

 Arguments:

      <aOptions> is the array to list.

      <cTitle> is an optional title.

      <nTop>,<nLeft>,<nBottom>,<nRight> Window Co-ords.

      <aValid> an array of logical values matching the
      options list.

      <nStartItem> is the entry point for the array.

      <nStartRow> is the row of the window to start on.

 Returns:

      nSelected

 Description:

      Basically this is a tarted up ACHOICE(). Allowing
      a box around it, title and proper key handling.

 Examples:

      nOption := 1
      nOption := Gt_Choose({'1. Start','2. End  ','3.Exit '}, ;
          'Now what?',02,02,NIL,NIL,NIL,nOption)

 Source: GT_CHOOS.PRG

 Author:  Martin Bryant