Only one validition fair not multiple row in gridview in asp.net

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ASP.NET

jQuery

Hi...friend ...
i ma using this JQuery.
and Call to gridview templetfiled using Textbox.

$(function () {
        $("[id*=grvExam]").each(function (e) {
            $("[id*=grvExam]input[type=text][id*=txtMark]").keydown(function (e) {
                if (e.shiftKey || e.ctrlKey || e.altKey) {
                    e.preventDefault();
                } else {
                    var key = e.keyCode;
                    if (!((key == 8) || (key == 46) || (key >= 35 && key <= 40) || (key >= 48 && key <= 57) || (key >= 96 && key <= 105) || (key >= 65 && key <= 66))) {
                        e.preventDefault();
                    }
                }
            })
        })
    })

Gridview...

<asp:GridView ID="grvExam" runat="server" AutoGenerateColumns="False" CellPadding="0"
                          CssClass="GridViewStyle" Width="70%" AllowPaging="True" PageSize="50">
                          <pagersettings mode="NextPreviousFirstLast" firstpagetext="  First  |" lastpagetext="  Last  |">
                              NextPageText="  Next  |" PreviousPageText="  Prev  |" />
                          <pagerstyle horizontalalign="Center" />
                          <footerstyle backcolor="White" forecolor="#000066" />
                          <rowstyle cssclass="GridViewRowStyle" />
                          <columns>
                              <asp:TemplateField HeaderText="Mark">
                                  <itemtemplate>
                                      <asp:TextBox ID="txtMark" runat="server" Width="40%" AutoPostBack="true" Text='<%# bind("Exam_OutMark") %>'
                                          Style="text-transform: uppercase;" OnTextChanged="txtMark_TextChanged">
                                  </itemtemplate>
                                  <itemstyle width="15%" horizontalalign="Left" />

                              <asp:TemplateField HeaderText="ER No">
                                  <itemtemplate>
                                      <asp:Label ID="lbl_ER" runat="server" Text='<%# bind("Student_Rollno") %>'>
                                  </itemtemplate>
                                  <itemstyle width="10%" horizontalalign="Left" />



                          </columns>
                          <emptydatatemplate>
                              <div class="EmptyRowStyle">
                                  No Record Found.</div>
                          </emptydatatemplate>
                          <SelectedRowStyle CssClass="GridViewSelectedRowStyle" />
                          <HeaderStyle CssClass="GridViewHeaderStyle" />

Textbox validtion Not fair...

please help me...