Context-question

As script.aculo.us does not seem to be available these days, Im asking 
my question
instead of looking it up. :-)

Im making an Ajax.Request, but would like to maintain the context in the 
onComplete-function.
Fx.
----------------- SNIP ------------------------
function MyClass(){
   this.showMsg=function(msg){
       alert(msg);
   }
   this.myRequest=function(){
       var options={
           onComplete:function(t){
               this.showMsg("Request ended");
           }
       }
       new Ajax.Request("http://myserver";, options);
      this.showMsg("Request started");
  }
}
var test=new MyClass();
test.myRequest();
--------------- SNAP ---------------------------

Its just a dummy function - but it fails because onComplete does no
have the right context and therefore can not use this.showMsg().

Any of you guys know how to maintain context?

Best Regards
Michael Krog