Hi,
Tab labels do not support templates, however, you may set their Text which "contains" templates. For example, you may insert a button by something like
<Tabs>
<igtab:Tab Text="New Tab <input type='button' value='but' onclick='myClick()' />"></igtab:Tab>
...
</Tabs>
You may process that click event by following
function myClick()
{
var tb = document.getElementById('TextBox1');
if(tb)
tb += 'x'; //tb.value = 'postback by tab';
__doPostBack('TextBox1');
}
So, now on server you at least will get postback. If you have somewhere on page TextBox1 and you process its TextChange event, then that handler also should be hit.
Note: if you do similar, then there is no support in case of misbehavior or any side efffects.