Creating NTX index files in vb .net

I am using codebase 6.

I am facing problem in creating index file NTx. The source code used by
me is as under.

 Public Function reindexall()
    ' this function reindex all the database
      Try
        cb = code4init()
        rc = code4autoOpen(cb, 0)
        rc = code4accessMode(cb, OPEN4DENY_RW)  'open file exclusively
to speed pack
        ltrlist1()
        rc = d4close(db)


        rc = code4initUndo(cb)

        'error4exitTest(cb)
        'rc = code4optStart(cb)
        'rc = d4top(db)
        'Do While rc = r4success
        '    Call d4delete(db)          'mark record for deletion
        '    rc = d4skip(db, 1)
        'Loop
        'physically remove the deleted records from the disk

      Catch ex As Exception
        MessageBox.Show(ex.Message)

      End Try
      '        rc = d4pack(db)
      'code4close(cb)
      cb = Nothing
      db = Nothing
      rc = Nothing
  End Function

  Public Sub ltrlist1()
    Dim tagInfo(0) As TAG4INFO
    tagInfo(0).name = "LTRLIST"
    tagInfo(0).expression = "INV_ID"

    db = d4open(cb, MainFrm.RootPath + "\DAY_ORD\LTRLIST")
    index = i4create(db, "", tagInfo)
    rc = d4close(db)

  End Sub

in vb .net I am unable to set a lower bound for array declaration. Whe
I run this programme, I get a message

Error : -20
Error : 90602
creating file
file4create
0.cgp

can any one help with an example of creating index file (NTX) in VB
..net 2003

TIA

Natwar Lath