You could also make a second request to your own web server and forward any headers the script will need.
Alternately, you might be able to solve this with an <img src="http://whatever.com/page_with_counter_include.shtml" width=0 height=0>.
Alternately, you might be able to solve this with an <img src="http://whatever.com/page_with_counter_include.shtml" width=0 height=0>.