Can't Find OnChange= event, Undefined

I have an OnChange event that I want to call, yet I keep getting a message that it is undefined.

I have the code in a script tage with a runat=server.  It worked prior to moving it to the "server" area.  I moved it there because I actually need to update via a code file too.

<%@ Control Language="VB" AutoEventWireup="true" CodeFile="claim_auto.ascx.vb" Inherits="KeyLimeTie.CMS.Web.Common_UserControls_Custom_claim_auto" %>


<script runat="server">
    Sub change_Primary_Message(ByVal Source As Object, ByVal e As EventArgs)
        If (Not Primary_Type.SelectedIndex = 0) Then
            Primary_Message_Row.Visible = True
        Else
            Primary_Message_Row.Visible = False
        End If
    End Sub
    
    Sub change_Secondary_Message(ByVal Source As Object, ByVal e As EventArgs)
        If (Not Secondary_Type.SelectedIndex = 0) Then
            Secondary_Message_Row.Visible = True
            Secondary_Name_Label.Text = "(required)"
        Else
            Secondary_Message_Row.Visible = False
            Secondary_Name_Label.Text = ""
        End If
    End Sub
</script>

<asp:DropDownList id="Secondary_Type" runat="server" OnChange="change_Secondary_Message"></asp:DropDownList>

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Thanks In Advance,