[1.0] HTTP Response Content-Type Mis-Match

Code:

---

HTTP/1.1 200 OK
Cache-Control: private
Content-Type: text/html; charset=utf-8
Date: Wed, 30 Mar 2011 19:34:13 GMT
Content-Length: 289
{script:"Window1.hide();Viewport1.removeAll();Viewport1.add({id:\"Panel10\",layout:\"fit\",autoLoad:{url:\"/FRP/IntPos/PositionInst.aspx\",nocache:true,scripts:true,mode:\"iframe\",showMask:true},border:false,padding:\"1 1 1 1\"});Panel10.paddingSummary=\"1 1 1 1\";Viewport1.doLayout();"}

---

How do I change response content-type to application/Json after Directevent post?

Here is a related thread.
http://forums.ext.net/showthread.php?38601