How to add a cookie header in response headers when do external redirect?

[Whut Jia]

Hi,
I want to save accessed uri into response cookie before doing a external 
redirect,according this way below:
 apr_table_setn(r->headers_out,"Location","http://www.idp.com/login.jsp";);
apr_table_setn(r->headers_out,"Set-Cookie",r->uri);
return HTTP_SEE_OTHER;
But in client ,I cannot always find cookie header in response headers ，why  
?How do I solve this??
Thanks,
ajxs