Set viewstate variable at end of page lifecycle

[tut365]

What am I trying to do is to set a ViewState variable at the end of a page lifecycle: what I have, is completely loaded asp.net page - communicating with AJAX calls with client JavaScript... when the ajax call from the client JavaScript is performed, some C# methods from the server code are executed. During this execution, I want to set a ViewState variable and use it on the next postback, but apparently the ViewState variable is not stored - because the page is completely loaded - all logic is performed at the end of the page lifecycle.I've tried explicitly calling these methods before and after setting the ViewState variable:\[code\] this.TrackViewState(); if (startAddr != "") { ViewState["startAddress"] = startAddr; } this.SaveViewState();\[/code\]But with no success... on the next postback, the \[code\]ViewState["startAddress"]\[/code\] is null.Any suggestions, if the above described functionality can be achieved?!Thanks!