Here's that Ajax call wrapper...

1. function InitiateAjaxRequest(url, callBack)    
2. {    
3.   var http = getHTTPObject(); // Create the HTTP Object    
4.     
5.   http.onreadystatechange = function()    
6.   {    
7.     if ((http.readyState == 4) && (http.status == 200))    
8.       callBack(http.responseText);    
9.   };    
10.   
11.   http.open("GET", url, true);    
12.   http.send(null);    
13. }    

So now, all I have to do on the page is...

1. function onSomeUIEvent()    
2. {    
3.   InitiateAjaxRequest("someBusinuessPage.aspx?CustID=42", onRecvdCustDetails);    
4. }    
5.      
6. function onRecvdCustDetails(responseText)    
7. {    
8.   // do something with reponseText  
9. }    

Suh-weet.