Writing Data to an Existing Excel File

[Sean04]

Try this..

        Dim xlApp As Excel.Application = DirectCast(CreateObject("Excel.Application"), Excel.Application)
        Dim xlAppWorkbook As Excel.Workbook = DirectCast(xlApp.Workbooks.Add(), Excel.Workbook)

        'Add textbox value to cell A1
        xlApp.Range("A1").Value = TextBox1.Text
        xlApp.Range("B1").Value = TextBox2.Text
        xlApp.Range("A1").Value = TextBox3.Text
        xlApp.Range("C1").Value = TextBox4.Text
        xlApp.Range("D1").Value = TextBox5.Text
        'and so on...
        xlApp.Visible = True

Make sure you include the Microsoft.Office.Interop.Excel reference

And add this:

Imports Microsoft.Office.Interop