Only one check box to be selected at any one time in gridview

i have added a check box on my grid view. how do i make it so only 1 check box can be selected at any time.

                    <asp:GridView ID="GridView3" runat="server" AutoGenerateColumns="False" Font-Size="Small" Width="100%">
                        <Columns>


                            <asp:BoundField DataField="Supplier" HeaderText="Supplier" SortExpression="Supplier" />
                            <asp:BoundField DataField="Term" HeaderText="Term" SortExpression="Term" />
                            <asp:BoundField DataField="Tariff" HeaderText="Tariff" SortExpression="Tariff" />
                            <asp:BoundField DataField="SC" HeaderText="SC" SortExpression="SC" />
                            <asp:BoundField DataField="Charge" HeaderText="Charge" SortExpression="Charge" />
                            <asp:BoundField DataField="Unit_Rate" HeaderText="Unit_Rate" SortExpression="Unit_Rate" />
                            <asp:BoundField DataField="Day_Rate" HeaderText="Day_Rate" SortExpression="Day_Rate" />
                            <asp:BoundField DataField="Night_Rate" HeaderText="Night_Rate" SortExpression="Night_Rate" />
                            <asp:BoundField DataField="Weekday_Rate" HeaderText="Weekday_Rate" SortExpression="Weekday_Rate" />
                            <asp:BoundField DataField="Eve_Wkend_Rate" HeaderText="Eve_Wkend_Rate" SortExpression="Eve_Wkend_Rate" />
                            <asp:BoundField DataField="Eve_Wkend_Night_Rate" HeaderText="Eve_Wkend_Night_Rate" SortExpression="Eve_Wkend_Night_Rate" />
                            <asp:BoundField DataField="Winter_Rate" HeaderText="Winter_Rate" SortExpression="Winter_Rate" />
                            <asp:BoundField DataField="Other_Rates" HeaderText="Other_Rates" SortExpression="Other_Rates" />
                            <asp:BoundField DataField="ID" HeaderText="ID" SortExpression="ID" />
                            <asp:TemplateField>
                                <ItemTemplate>
                                    <asp:CheckBox ID="CheckBox1" runat="server" />
                                </ItemTemplate>
                            </asp:TemplateField>