Modify locations header in reverse proxy

Hi

I am testing Nginx as a reverse proxy to replace our aging TMG server and I have got most functions running. My issue is with one of our server.

When browsing to http://external.com/temse the upstream server responds with a location redirect (302)

http://internal.com:80/auth/?id=568607574B2BC6BA182B4DA7761EE245&target=http://internal.com:7400/&

I have managed to change the first part of the URL with the proxy_redirect directve

proxy_redirect http://internal.com:80/ /temseauth/;

so i will get the location URL

http://external.com/temseauth//auth/?id=568607574B2BC6BA182B4DA7761EE245&target=http://internal.com:7400/&

The problem i face is ia cannot modify the second url in the location header, "target=http://internal.com:7400/", it should be modified to "target=https:/external.com/temse/"

Anyone got an ideá what can be done?

below is the complete config:
upstream temse {
server 192.168.0.100:7400;
}

upstream temseauth {
server 192.168.0.100:80;
}

server {
listen *:80;
listen *:443 default ssl;
server_name external.com;
ssl_certificate /etc/nginx/ssl/nginx.crt;
ssl_certificate_key /etc/nginx/ssl/nginx.key;

if ($ssl_protocol = "") {
rewrite ^/(.*) https://$server_name$request_uri? permanent;
}


location /temseauth/ {

proxy_pass http://temseauth/;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Accept-Encoding "";
proxy_connect_timeout 180;
proxy_send_timeout 180;
proxy_read_timeout 180;

}




location /temse/ {

proxy_pass http://temse/;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Accept-Encoding "";
proxy_redirect http://internal.com:80/ /temseauth/;

proxy_connect_timeout 180;
proxy_send_timeout 180;
proxy_read_timeout 180;

}
}


/Ulf