Force a postback inside a WebMethod

I am using a 3rd party control for GIS map related functions. I had the need to call a C# Method from within javascript. I chose to use PageMethods like this:

PageMethods.getFeature(x,y)

Works like a charm as long as you convert your method to a [WebMethod]

In this method I am passing in the coordinates of the mouse and it returns me map features. That I will highlight on the map.

From researching I found that you cant directly access the UI from inside a [WebMethod] so I decided to set a session variable and postback. On postback if the session variables exist I would make the necessary UI changes.

My WebMethod looks like this:

[WebMethod(EnableSession = true)]
        public static void getFeature(float x, float y)
        {...
        some code in here. 
        }

Update This is my jQUery:

  <script>
        $(document).ready(function (e) {
            $(".MyMap").click(function (e) {
                var posX = $(this).position().left;
                var posY = $(this).position().top;
                PageMethods.getFeature(e.pageX-posX, e.pageY-posY);
              });
        });
    </script>

How do I force a postback inside of a WebMethod. Most of the ways I know to postback don't work.

Solution

Special Thanks to @BenRobinson for assisting me in the right direction. Here is what I came up with. I am posting this for other people who may make a similar mistake. The short answer is: **You Cant

My main issue was I was using a [WebMethod] so my c# code could be called from jQuery. This worked perfectly until I needed access to the UI. Well technically a 'WebMethod' is almost like calling a web service. You cant have a remote web service update the UI. What you can do is after your function in jQuery runs that calls the [WebMethod], is have it call a new page (window.location). That location can call the original page (in my case Default.aspx). I passed parameters in the request field that I needed to send to the UI, and I basically put code in that if on load you see a particular request variable then do something... It worked like a charm.

Here's a rough example: In my jQuery page I did this (to navigate to a new page):

window.location.replace("ZoomAndCenter.aspx?x=" + (e.pageX - posX) + "&y=" + (e.pageY - posY))

Here is what my ZoomAndCenter.aspx looked like:

protected void Page_Load(object sender, EventArgs e)
            {
                int x = 0;
                double y = 0;
                x = Int32.Parse(Request["x"].ToString());
                y = Double.Parse(Request["y"].ToString());
                //Run some more code
                Response.Redirect("Default.aspx?Param1=xxxx&Param2=xxxx");
                //passed the params in the redirect.
             }

Then in the Default.aspx

 if(request["param1"] == "something")
{
//do something
}