How to refresh Combobox items

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.NET

.NET4.5

Have several fields on windows form which inplement with comboboxes. I porpulate these comboboxes with datatble. The code is shown below. Everything works fine but there is one problem.

Public Sub getFamilyRel(cb As ComboBox)
        Try
            Dim CMD As New SqlClient.SqlCommand
            Dim dt As New DataTable
            CMD.CommandText = "select Code, code + ' - ' + description as Des from famrelup"
            CMD.CommandType = CommandType.Text
            Dim CN As New SqlClient.SqlConnection(My.Settings.cdataConnectionString.ToUpper)
            CMD.Connection = CN
            CN.Open()
            Dim RDR As New SqlClient.SqlDataAdapter
            RDR.SelectCommand = CMD
            RDR.Fill(dt)
            With cb
                .DataSource = dt
                .ValueMember = "code"
                .DisplayMember = "des"
            End With
        Catch ex As Exception
            MessageBox.Show(ex.Message, Application.ProductName, MessageBoxButtons.OK, MessageBoxIcon.Error)
        End Try
    End Sub

The problem is that I update the base tables that populate the comboboxes via modal forms and these updates do not show up in the comboboxes unless I reload the form which contains the comboboxes.

I wonder if anybody can help me to have the updates show up in the comboboxes lists without reloading the form.

I am using .NET 2012

Thanks for usual assistance