Can two OnclientClick fires on a single page?

<asp:Button ID="btnUpload" CssClass="myButton" runat="server" OnClick="btnUpload_Click" Text="Import Email Id's" OnClientClick="return ValidateFile()"/>
                    <script type="text/javascript">
                        //        var validFilesTypes = ["bmp", "gif", "png", "jpg", "jpeg", "doc", "xls"];
                        var validFilesTypes = ["xls", "xlsx"];
                        function ValidateFile() {
                            var file = document.getElementById("<%=FileUpload2.ClientID%>");
                            var label = document.getElementById("<%=Label1.ClientID%>");
                            var path = file.value;
                            var ext = path.substring(path.lastIndexOf(".") + 1, path.length).toLowerCase();
                            var isValidFile = false;
                            for (var i = 0; i < validFilesTypes.length; i++) {
                                if (ext == validFilesTypes[i]) {
                                    isValidFile = true;
                                    break;
                                }
                            }
                            if (!isValidFile) {
                                $(function ShowPopup(message) {
                                    $(function () {
                                        var message = "Invalid File. Please upload a File with" + " extension:\n\n" + validFilesTypes.join(", ");
                                        $("#dialog").html(message);
                                        $("#dialog").dialog({
                                            title: "Error",
                                            buttons: {
                                                Close: function () {
                                                    $(this).dialog('close');
                                                }
                                            },
                                            modal: true
                                        });
                                    });
                                });

                                label.style.color = "red";
                                label.innerHTML = "Invalid File. Please upload a File with" + " extension:\n\n" + validFilesTypes.join(", ");
                            }
                            return isValidFile;
                        }
                    </script>

 <script type="text/javascript">
                        $(function ValidatePg() {
                            var ToEmail = document.getElementById('<%=TxtTO.ClientID %>').value;
                            var Subject = document.getElementById('<%=TxtSubject.ClientID %>').value;
                            if (TxtTO == "") {
                                alert("No Email id Choosen, Please Enter Email ID");
                                document.getElementById('<%=TxtTO.ClientID %>').focus();
                                return false;
                            }
                            if (TxtSubject == "") {
                                var message = "EnterSubject";
                                ShowPopup(message);
                                alert("EnterSubject");
                                document.getElementById('<%=TxtSubject.ClientID %>').focus();
                                return false;
                            }
                            label.style.color = "red";
                            label.innerHTML = "Invalid File. Please upload a File with";
                        });
                    </script>
                    <asp:Button ID="Btn_Send" CssClass="myButton" runat="server" Text="Send" OnClick="Btn_Send_Click" OnClientClick="return ValidatePg()"/>