I used the Configure Data source wizard to bound my Grid. Now I want to make one column readonly when the Edit link is clicked. Not sure where I would set?

Code:
asp:GridView ID="gv" runat="server" DataSourceID="SqlDataSource1" 
        
        style="top: 630px; left: 21px; position: absolute; height: 133px; width: 861px" 
        AutoGenerateDeleteButton="True" AutoGenerateEditButton="True" 
        Font-Bold="False">
    
    
   
   </asp:gridview>
        
        <asp:SqlDataSource ID="SqlDataSource1" runat="server" 
        ConnectionString="<%$ ConnectionStrings:ConnectionString2 %>" 
        ProviderName="<%$ ConnectionStrings:ConnectionString2.ProviderName %>" 
        
        SelectCommand="SELECT &quot;SURPLUS_YR&quot;, &quot;DIV&quot;, &quot;SEQ_NO&quot;, &quot;SURPLUS_TYPE&quot;, &quot;DECAL_NO&quot;, &quot;FIELD_DESC&quot;, &quot;FIELD_MFGR&quot;, &quot;FIELD_SERIAL_NO&quot;, &quot;ITEM_CONDITION&quot;, &quot;SURPLUS_REASON&quot; FROM &quot;SPAR_DECAL_ITEM&quot; WHERE ((&quot;SURPLUS_YR&quot; = :SURPLUS_YR) AND (&quot;SEQ_NO&quot; = :SEQ_NO) AND (&quot;DIV&quot; = :DIV))" 
        DeleteCommand="DELETE FROM &quot;SPAR_DECAL_ITEM&quot; WHERE &quot;SURPLUS_YR&quot; = :SURPLUS_YR AND &quot;DIV&quot; = :DIV AND &quot;SEQ_NO&quot; = :SEQ_NO AND &quot;SURPLUS_TYPE&quot; = :SURPLUS_TYPE AND &quot;DECAL_NO&quot; = :DECAL_NO" 
        InsertCommand="INSERT INTO &quot;SPAR_DECAL_ITEM&quot; (&quot;SURPLUS_YR&quot;, &quot;DIV&quot;, &quot;SEQ_NO&quot;, &quot;SURPLUS_TYPE&quot;, &quot;DECAL_NO&quot;, &quot;FIELD_DESC&quot;, &quot;FIELD_MFGR&quot;, &quot;FIELD_SERIAL_NO&quot;, &quot;ITEM_CONDITION&quot;, &quot;SURPLUS_REASON&quot;) VALUES (:SURPLUS_YR, :DIV, :SEQ_NO, :SURPLUS_TYPE, :DECAL_NO, :FIELD_DESC, :FIELD_MFGR, :FIELD_SERIAL_NO, :ITEM_CONDITION, :SURPLUS_REASON)" 
        UpdateCommand="UPDATE &quot;SPAR_DECAL_ITEM&quot; SET &quot;FIELD_DESC&quot; = :FIELD_DESC, &quot;FIELD_MFGR&quot; = :FIELD_MFGR, &quot;FIELD_SERIAL_NO&quot; = :FIELD_SERIAL_NO, &quot;ITEM_CONDITION&quot; = :ITEM_CONDITION, &quot;SURPLUS_REASON&quot; = :SURPLUS_REASON WHERE &quot;SURPLUS_YR&quot; = :SURPLUS_YR AND &quot;DIV&quot; = :DIV AND &quot;SEQ_NO&quot; = :SEQ_NO AND &quot;SURPLUS_TYPE&quot; = :SURPLUS_TYPE AND &quot;DECAL_NO&quot; = :DECAL_NO">
        
        <SelectParameters>
            <asp:ControlParameter ControlID="txtYr" Name="SURPLUS_YR" PropertyName="Text" 
                Type="String"  />
            <asp:ControlParameter ControlID="txtSeqNo" Name="SEQ_NO" PropertyName="Text" 
                Type="String" />
            <asp:ControlParameter ControlID="txtDiv" Name="DIV" PropertyName="Text" 
                Type="String" />
        </SelectParameters>
        <DeleteParameters>
            <asp:Parameter Name="SURPLUS_YR" Type="String" />
            <asp:Parameter Name="DIV" Type="String" />
            <asp:Parameter Name="SEQ_NO" Type="String" />
            <asp:Parameter Name="SURPLUS_TYPE" Type="String" />
            <asp:Parameter Name="DECAL_NO" Type="Decimal" />
        </DeleteParameters>
        <UpdateParameters>