Changing the tab index of AJAX Tab control through Javascript

function SetActiveTab(tabControl, tabNumber)
{
  var ctrl = $find(tabControl);
  ctrl.set_activeTab(ctrl.get_tabs()[tabNumber]);
}

Here 
1.tabControl is client id of tabcontainer.
2.tabNumber is tab index as numeric


to pass Client ID use this

<input type="Button" onClick="SetActiveTab('<%=tabControl.ClientID%>',2);"
value="Next"> </input>