Hi, I am looking write a javascript method as such called when a dropdownlist changes value

function GetStuff(sender, destID){

    var dest = document.getElementById(destID);
    this.PageMethods.GetStuffs(sender, dest, null, null);
}

GetStuffs() is in the Codebehind as follows:

[WebMethod]
public static void GetStuffs(object sender, object dest)
{
    DropDownList s = sender as DropDownList;
    DropDownList d = dest as DropDownList;

    d.Items.Add(new ListItem(s.SelectedValue));
}

I have a break point set at the method and alerts in the GetStuff() jscript method fire up until the PageMethod call, at which nothing happens. I have set OnSuccess and OnFailure methods up with alerts and they don't get fired.

Any thoughts? Am I doing something inherently wrong?