Probelm with use TSHttpHdrUrlSet

[ChangCheng]

Hi users;i want to set url(www.example.com) for http header, how do i use 
TSHttpHdrUrlSet. the prototype is :TSReturnCode TSHttpHdrUrlSet (INKMBuffer 
bufp, INKMLoc hdr_loc, INKMLoc url)the problem is INKMloc url is object, how do 
i sign my url value(char *) to this object?Thanks