Form HTML5 execute method in codebehind to go to another page after doing a submit with button

I have a form where I use HTML5 elements and take advantage of HTML5 validation. At the time of submitting with 'button' I need to call a codebehind function first so I can jump to another page. I can not put in the action of the form the page I want to go to or function since I use scriptManager because I do several postback

<form id="form1" name="form1" runat="server" action="" >
  <asp:ScriptManager ID="scm_Paso1" runat="server" ></asp:ScriptManager>
    <asp:UpdatePanel ID="upn1" runat="server" UpdateMode="Conditional"> 
    <ContentTemplate> 
      <div class="container">  
        <input type="text" required  ID="txtFecha" runat="server" />
      </div>
    </ContentTemplate>
    </asp:UpdatePanel>
      <div class="container">
        <button id="btnContinuar" runat="server" onclick=""></button>
      </div>
</form>