Assign Drop Down list value to textbox Visual Basic

I have an ad sales application that has a series of checkboxes.  One checkbox asks the sales rep if the order is a multiple company listing.  If it is the following information fires:  I need to somehow get the value of the dropdown list      ddMultipleRate.SelectedValue = "47" to also show in the textbox         (  txtMultipleRate.text )


    Protected Sub txtMultiple_CheckedChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtMultiple.CheckedChanged
        If txtMultiple.Checked = True Then
            lblSecondary.Text = "Secondary Company Name:"
            lblSecondary.ToolTip = "Enter in Secondary company name as it is to be shown in directory/web"
            lblMultipleIn.Visible = True
            txtMultipleIn.Visible = True
            lblMultipleRate.Visible = True
            ddMultipleRate.Visible = True
            ddMultipleRate.SelectedValue = "47"
            txtMultipleRate.Visible = True
            lblMultipleOverride.Visible = True
            txtMultipleRateOverride.Visible = True


        Else
            lblSecondary.Text = "Other Advertiser:"
            lblSecondary.ToolTip = "Not Exhibiting or sharing a booth, list company name"
            lblMultipleIn.Visible = False
            txtMultipleIn.Visible = False
            lblMultipleRate.Visible = False
            ddMultipleRate.Visible = False
            txtMultipleRate.Visible = False
            lblMultipleOverride.Visible = False
            txtMultipleRateOverride.Visible = False
        End If
    End Sub