Range Validation in ASP.Net GridView row Editing using C# and VB.Net

I have an updatable GridView that update the Merk field by using jQuery.

Now I want to Check the value of Mark filed in GridView and I want to Restricts the user to entering numbers from 0 to 20. And Avoid inserting Mark < 0 And Mark > 20

How Can I do this truly:

            <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" BackColor="White" BorderColor="#CCCCCC" BorderStyle="None" BorderWidth="1px" CellPadding="3" DataSourceID="SqlDataSrcAddMark" Font-Names="Tahoma" HorizontalAlign="Center" Width="800px" OnSelectedIndexChanged="GridView1_SelectedIndexChanged">
                <Columns>
                    <asp:TemplateField HeaderStyle-CssClass="Header-center" HeaderText="نمره" ItemStyle-Width="200px" SortExpression="Mark">
                        <ItemTemplate>
                            <asp:Label ID="lbl_Text1" runat="server" Text='<%# Bind("Mark") %>'></asp:Label>
                            <asp:TextBox ID="txt_Text1" runat="server" AutoPostBack="true" CssClass="hideControl" OnTextChanged="Change" Text='<%# Bind("Mark") %>'></asp:TextBox>
                        </ItemTemplate>
                        <HeaderStyle CssClass="Header-center" />
                        <ItemStyle Width="200px" />
                    </asp:TemplateField>
                    <asp:TemplateField HeaderText="ExamAttendanceTypeId " SortExpression="ExamAttendanceTypeId">
                        <EditItemTemplate>
                            <asp:TextBox ID="TextBox1" runat="server" ReadOnly="true" Text='<%# Bind("ExamAttendanceTypeId") %>'></asp:TextBox>
                        </EditItemTemplate>
                        <ItemTemplate>
                            <asp:Label ID="Label1" runat="server" Text='<%#Bind("ExamAttendanceTypeId") %>'></asp:Label>
                        </ItemTemplate>
                        <HeaderStyle CssClass="Header-center" />
                    </asp:TemplateField>
                    <asp:BoundField DataField="LastName" HeaderStyle-CssClass="Header-center" HeaderText="LastName" SortExpression="LastName">
                    <HeaderStyle CssClass="Header-center" />
                    </asp:BoundField>
                    <asp:BoundField DataField="FirstName" HeaderStyle-CssClass="Header-center" HeaderText="FirstName " SortExpression="FirstName">
                    <HeaderStyle CssClass="Header-center" />
                    </asp:BoundField>
                    <asp:BoundField DataField="LessonTitle" HeaderStyle-CssClass="Header-center" HeaderText="LessonTitle " SortExpression="LessonTitle">
                    <HeaderStyle CssClass="Header-center" />
                    </asp:BoundField>
                    <asp:BoundField DataField="StudentId" HeaderStyle-CssClass="Header-center" HeaderText="StudentId" SortExpression="StudentId">
                    <HeaderStyle CssClass="Header-center" />
                    </asp:BoundField>
                </Columns>               
            </asp:GridView>

             <asp:SqlDataSource ID="SqlDataSrcAddMark" runat="server" ConnectionString="<%$ ConnectionStrings:KDUIS-v1ConnectionString %>" OnUpdating="SqlDataSrcAddMark_Updating" SelectCommand="ShowPresentStudent" SelectCommandType="StoredProcedure" UpdateCommand="UPDATE [EDU_Student_Course_Registration] SET [Mark] = @Mark 
                 WHERE [StudentId] = @StudentId AND [SubjectStudyLessonCourseId]=@SubjectStudyLessonCourseId ">
                <SelectParameters>
                    <asp:ControlParameter ControlID="SubjectStudyLessonCourseId" Name="CourseId" PropertyName="Text" Type="Int32" />
                </SelectParameters>
                <UpdateParameters>
                    <asp:Parameter Name="Mark" Type="Double" />
                    <asp:Parameter Name="StudentId" />
                    <asp:Parameter Name="SubjectStudyLessonCourseId" Type="Int32" />
                </UpdateParameters>
            </asp:SqlDataSource>

        protected void Change(object sender, EventArgs e)
        {
            Person obj = new Person();
            TextBox txtMark = sender as TextBox;
            string mark = txtMark.Text;

            //ShowMarkResult(Convert.ToInt32(mark));
            GridViewRow row = (GridViewRow)txtMark.NamingContainer;
            string MarkStatusId = "2";
            //string status = (row.FindControl("hfStatus") as HiddenField).Value.Trim();
            string query = "UPDATE EDU_Student_Course_Registration SET Mark = @Mark, MarkDate=@MarkDate, MarkStatusId=@MarkStatusId," +
                " MarkResaultId=@MarkResaultId WHERE StudentId = @StudentId AND SubjectStudyLessonCourseId = @SubjectStudyLessonCourseId";
            string constr = ConfigurationManager.ConnectionStrings["KDUIS-v1ConnectionString"].ConnectionString;
            using (SqlConnection con = new SqlConnection(constr))
            {
                using (SqlCommand cmd = new SqlCommand(query, con))
                {
                    cmd.Parameters.AddWithValue("@Mark", txtMark.Text);
                    cmd.Parameters.AddWithValue("@MarkDate", obj.CreateDateTime());
                    cmd.Parameters.AddWithValue("@MarkStatusId", MarkStatusId);
                    cmd.Parameters.AddWithValue("@MarkResaultId", Convert.ToDouble(mark));
                    cmd.Parameters.AddWithValue("@SubjectStudyLessonCourseId", SubjectStudyLessonCourseId.Text);
                    cmd.Parameters.AddWithValue("@StudentId", row.Cells[5].Text);

                    con.Open();
                    cmd.ExecuteNonQuery();
                    con.Close();
                    GridView1.DataBind();
                }
            }
        }