Bubble The Value To The Form - VS 2010 Delegates?

I have a standard web app. My default page has a WebMethod and the WebMethod gets invoked by Json from client script. On my webForm I have an area that displays messages to the user showing the stage in the process and this is just a <asp:label>. if The webmethod had been a standard method, I would simply have done something like myLabel.Text = "sometext". However, the webMethod knows nothing about the label and so I need to bubble the value to the form. If I had called the webmethod from the codebehind in the form I may have been able to use delegates/events, but the call was made by the client, so I have not wired the webmethod up to any codebehind. How do I push my text back to the form in an asyncronous manner. So the code works in this way: Form load populates some controls on the client. The user perfoms some drag and drop then presses a standard html input button that calls a client ajax/json method passing the dragged values to the webmethod. I then need to feed back to the screen at several points in the webmethod process to inform the user of the current status.