Update Dropdown button values at runtime

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VB

MS-Excel

forms

dataset

Hi i have a dropdown box with a datasource from an excel file.I fill my dropdown box with that code

System.Windows.Forms.Application.EnableVisualStyles()
    ' This call is required by the designer.
    InitializeComponent()
    ' Add any initialization after the InitializeComponent() call.

    Dim a As New OleDbConnectionStringBuilder With
        {.Provider = "Microsoft.ACE.OLEDB.12.0",
            .DataSource = IO.Path.Combine(My.Settings.CargoData, "CargoData.xlsx")
            }
    a.Add("Extended Properties", "Excel 12.0; HDR=Yes;")
    Dim SheetName_2 As String = "CargoData"
    Dim dt_2 As New DataTable
    Using cn_2 As New OleDbConnection With
        {
            .ConnectionString = a.ConnectionString
        }
        cn_2.Open()
        Dim cmd_2 As OleDbCommand = New OleDbCommand(
            <Text>
                SELECT 

                   Type  
                FROM [<%= SheetName_2 %>$] order by Type
            </Text>.Value,
            cn_2
        )
        Cargodt.Load(cmd_2.ExecuteReader)
    End Using

that code is in another form from my dropdown box.It's in frmMain. In dropdown form frmCargo i have this code

Private Sub frmCargo_Load(sender As Object, e As EventArgs) Handles Me.Load
    drpCargoType.DisplayMember = "Type"
    drpCargoType.DataSource = Cargodt
End Sub
Private Sub txtCargoType_KeyDown(sender As Object, e As KeyEventArgs) Handles txtCargoType.KeyDown
    If e.KeyCode = Keys.Enter Then
        Dim objExcel As New Excel.Application     ' Represents an instance of Excel
        Dim objWorkbook As Excel.Workbook     'Represents a workbook object
        Dim objWorksheet As Excel.Worksheet     'Represents a worksheet object
        objWorkbook = objExcel.Workbooks.Add
        objWorkbook = objExcel.Workbooks.Open("C:\Position Reports SBLK\Cargo Data\CargoData.xlsx")
        objWorksheet = CType(objWorkbook.Worksheets.Item("CargoData"), Excel.Worksheet)
        Dim lastRow As Long
        lastRow = objWorksheet.Range("A" & objExcel.Rows.CountLarge).End(Excel.XlDirection.xlUp).Row + 1
        With objWorksheet
            .Range("A" & lastRow).Value = txtCargoType.Text
        End With
        objWorkbook.Save()
        objWorkbook.Close(False)
        objExcel.Quit()
        txtCargoType.Hide()
        drpCargoType.Show()
    ElseIf e.KeyCode = Keys.Escape Then
        txtCargoType.Hide()
        drpCargoType.Show()
    End If
End Sub

The above code shows a textbox to add value in my worksheet,that works great,but i want at the same time to update the dropbox with the new added value.Please help.Also i have a code with a button that calls that textbox but i think its irrelevant