Ok I think I have changed the path for apache so that suexec is working... how can I check this. Thanks
Enable SuExec in ISPConfig and then use a cgi script that e.g. creates a file in the web directory. If this file is owned by the web admin and not the httpd user, SuExec is enabled successfully.
You can also try to run the "Hello world" Perl script from here: http://www.howtoforge.com/forums/showthread.php?t=171 If the script has the wrong owner and group, you should get an error from Apache (usually "500 Internal Server Error").