Getting the ClientID of ASP.NET server controls in external .js files

Hi,

In the aspx webform, I can put this:

  --- Javascript in ASPX:

function methodCompleted(results, context, methodName) {


            $get("<%=Button1.ClientID%>").disabled = false;
            $get("<%=lblHora.ClientID%>").innerHTML = results.toString();
 }

function getTimeBtnClicked(sender) {
    sender.disabled = true;
    PageMethods.GetTime(methodCompleted);
}

 [WebMethod]
 public static DateTime GetTime()
 {
     return DateTime.Now;
 }

And it works, I mean, I get the clientId of the server controls in runtime.

But the same code, in a external .js file, doesn't work.

Question 1
Obviuosly I prefer to have the javascript code on external .js files, it is possible to use <%=%> in a external .js file and execute it as a server side code?

Question 2
Is it possible to pass information of the sender object to the "methodCompleted" callback as a parameter?

Thanks!