Hi,

There is no server option to do that. However, you may process and cancel event on client if fields are not field or have wrong values. Example:

<script type="text/javascript">
function UltraWebTab1_BeforeSelectedTabChange(oWebTab, oTab, oEvent)
{
 var oldTab = oWebTab.getSelectedTab();
 if(oldTab.getIndex() == 0)
 {
    var text1 = oldTab.findControl("TextBox1");
    var text2 = oldTab.findControl("TextBox2");
    if(!text1 || !text2)
    {
        alert("can not find fields in tab 0");
        return;
    }
    if(text1.value.length < 1 || text2.value.length < 1)
    {
       alert("Text1:" + text1.value + " text2:" + text2.value);
       oEvent.cancel = true;
    }
 }
 if(oldTab.getIndex() == 1)
 {
    var text3 = oldTab.findControl("TextBox3");
    var text4 = oldTab.findControl("TextBox4");
    if(!text3 || !text4)
    {
      alert("can not find fields in tab 1");
      return;
    }
    if(text3.value.length < 1 || text4.value.length < 1)
    {
      alert("Text3:" + text3.value + " text4:" + text4.value);
      oEvent.cancel = true;
    }
 }
}
</script>

<igtab:UltraWebTab ID="UltraWebTab1" runat="server">
   <ClientSideEvents BeforeSelectedTabChange="UltraWebTab1_BeforeSelectedTabChange" />
   <Tabs>
     <igtab:Tab Text="New Tab">
       <ContentTemplate>
         <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
         <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
      </ContentTemplate>
    </igtab:Tab>
    <igtab:Tab Text="New Tab">
       <ContentTemplate>
         <asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
         <asp:TextBox ID="TextBox4" runat="server"></asp:TextBox>
      </ContentTemplate>
   </igtab:Tab>
  </Tabs>
</igtab:UltraWebTab>