asp.net asp:UpdatePanel and form submit java validation script

asp.net updatepanel I am working on a asp.net form where it got a javascript validation on form submit <form id="form2" runat="server" onsubmit="return validateForm();">

with in the form  i am using a  asp update panel <asp:UpdatePanel runat="server">                         <ContentTemplate>                             <div class="multiInput" id="departmentMenus"/>                                                        <table > . . <asp:Button ID="BtnSelect" runat="server"  Text=">>"                                     onclick="BtnSelect_Click" ></asp:Button>                              <asp:Button ID="btnDeselect" runat="server"  Text="<<"                                     onclick="btnDeselect_Click" ></asp:Button>

</ContentTemplate> </asp:UpdatePanel> now when i clicked on the  BtnSelect" or button btnDeselect i expect the update panle to do a self update but it is it send a full form post back and run the java scrip validation can some one help me out please thanks a lot for your assistance