save listview data to same excel file but different sheet

[sigridish]

i already know how to save in excel using openfiledialog. but what i want to happen is that when i save another file, i want it to be saved in my existing file but in a different sheet. can you guys help me?

this is my code for saving

Public Sub saveExcelFile(ByVal FileName As String)
            Dim xls As New Excel.Application
            Dim sheet As Excel.Worksheet
            Dim i As Integer
            xls.Workbooks.Add()
            sheet = xls.ActiveWorkbook.ActiveSheet
            Dim row As Integer = 1
            Dim col As Integer = 1
            For Each item As ListViewItem In ListView1.Items
                    For i = 0 To item.SubItems.Count - 1
                            sheet.Cells(row, col) = item.SubItems(i).Text
                            col = col + 1
                    Next
                    row += 1
                    col = 1
            Next
            xls.ActiveWorkbook.SaveAs(FileName)
            xls.Workbooks.Close()
            xls.Quit()
    End Sub


Private Sub btnsave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnsave.Click
            Dim saveFileDialog1 As New SaveFileDialog
            saveFileDialog1.Filter = "Excel File|*.xlsx"
            saveFileDialog1.Title = "Save an Excel File"
            saveFileDialog1.ShowDialog()
            If saveFileDialog1.FileName <> "" Then
                    saveExcelFile(saveFileDialog1.FileName)
            End If
            MessageBox.Show("Record Saved!")
    End Sub

[pod]

if fileExist then
  workbook.open file
  worksheet.add sheet
  put content in sheet
  save and close workbook
else
  workbook.add new book
  put content in activesheet
  save and close workbook
end if