You can try this in your web form with a button called btnSave for example:
<input type="button" id="btnSave" onclick="javascript:SaveWithParameter('Hello Michael')" value="click me"/> <script type="text/javascript"> function SaveWithParameter(parameter) { __doPostBack('btnSave', parameter) } </script>
And in your code behind add something like this to read the value and operate upon it:
public void Page_Load(object sender, EventArgs e) { string parameter = Request["__EVENTARGUMENT"]; // parameter // Request["__EVENTTARGET"]; // btnSave }
Give that a try and let us know if that worked for you.