clientclick to validate server side input

Hi Experts,

I have simple <form id="myform" runat="server" action="#">

<input id="mytxt1" runat="server" />
<input id="mytxt2" runat="server" />

<asp:button id="mybutton" onclick="do_stuff" onclientclick="something">
</form>

I need using either jquery or javascript to on clientclick code on client side :

1. get value of mytxt1
2  copy this value to mytxt2

Thanks a lot.