asp.net updatepanel  update sqldatasource

I have  a grid in an updatepanel that is bound to a sql datasource.

The sql datasource uses a stored procedure and I have the parameter value coming from a text field.

when the user clicks on a button I want to have the sql data source to update

How do I do this

<asp:SqlDataSource ID="SqlDataSource1" runat="server" 
        ConnectionString="<%$ ConnectionStrings:ConnectionString %>" 
        SelectCommand="usp_Admin_GetAll" 
        SelectCommandType="StoredProcedure" 
        ProviderName="<%$ ConnectionStrings:on.ProviderName %>">
        <SelectParameters>
            <asp:FormParameter DefaultValue="%" FormField="txtSearch" Name="txt" 
                Type="String" />
        </SelectParameters>
    </asp:SqlDataSource>

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