Export datagridview to excel

I create a program for events booking using VB.Net and access as database. So I want to export datagridview to excel for further user's editing. I coded the button called export. But when I click button it open save dialog box for me to save the data. But when I open the saved data in excel, only first column header appear as well as first row data information. The rest of the columns and other rows is not there. I attached the code I have used.

Imports System.Data.DataTable
Imports Excel = Microsoft.Office.Interop.Excel
Imports Microsoft.Office
Imports Microsoft.Office.Interop
Imports System.IO
Public Class Form1

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    End Sub

     Private Sub SaveBtn_Click(sender As Object, e As EventArgs) Handles SaveBtn.Click
        SaveToExcel()
    End Sub

    Private Sub SaveToExcel()
        Dim excel As Microsoft.Office.Interop.Excel._Application = New Microsoft.Office.Interop.Excel.Application()
        Dim workbook As Microsoft.Office.Interop.Excel._Workbook = excel.Workbooks.Add(Type.Missing)
        Dim worksheet As Microsoft.Office.Interop.Excel._Worksheet = Nothing

        Try

            worksheet = workbook.ActiveSheet
            worksheet.Name = "ExportedFromDatGrid"

            Dim CellRowIndex As Integer = 1
            Dim cellColumnIndex As Integer = 1

            For J As Integer = 0 To DataGridView1.ColumnCount = -1
                worksheet.cells(CellRowIndex, cellColumnIndex) = DataGridView1.Columns(J).HeaderText
                cellColumnIndex += 1

            Next
            cellColumnIndex = 1
            CellRowIndex += 1

            For i As Integer = 0 To DataGridView1.Rows.Count = -2
                For J As Integer = 0 To DataGridView1.ColumnCount - 1
                    worksheet.cells(CellRowIndex, cellColumnIndex) = DataGridView1.Rows(i).Cells(J).Value.ToString()
                    cellColumnIndex += 1


                Next
                cellColumnIndex = 1
                CellRowIndex += 1
            Next
            Dim SaveDialog As New SaveFileDialog()
            SaveDialog.Filter = "Excel Files(*.xlsx)|*.xlsx|All files (*.*)|*.*"
            SaveDialog.FilterIndex = 2

            If SaveDialog.ShowDialog() = System.Windows.Forms.DialogResult.OK Then
                workbook.saveAs(SaveDialog.FileName)
                MessageBox.Show("Export Successful")
            End If

        Catch ex As Exception
            MessageBox.Show(ex.Message)
        Finally
            excel.Quit()
            workbook = Nothing
            excel = Nothing
        End Try



    End Sub

    Private Sub SaveFileDialog1_FileOk(sender As Object, e As System.ComponentModel.CancelEventArgs)

    End Sub
End Class