How to impersonate request submitted to Certificate Authority Service?

Hi,I am accessing the CA service using following  code snippet from a sample console application. I was able to create the certificate request but when I submitted the same I got following error."CCertRequest::Submit Access is denied. 0x80070005 (WIN32: 5)" 
 
 XENROLLLib.CEnroll certEnroll = new XENROLLLib.CEnro ...