You're going to have to write a script in linux that runs check_nt, then performs something based on its output. This is linux, you are not restricted to pre-built binary functions.
your service definition has a new check_command:
Then heres your checkcommand:
command_line /usr/local/nagios/libexec/check_nt_load_script.sh $HOSTADDRESS$
This will run /usr/local/nagios/libexec/check_nt_load_script.sh , passing the HOSTADDRESS ip to it. This gets registered as $1 .
Heres a check_nt_load_script.sh example:
Wild guess on the check_nt parameters needed here cause i don't use it.. modify as necessary
/usr/local/nagios/libexec/check_nt -H $1 -c load -l 1,5,6
This is gonna throw back a return code of 0 (OK), 1 (WARNING), or 2 (CRITICAL). this return code gets thrown into the default variable called $?. We want to swap, if load is CRITICAL that is GOOD right? yeah!
if "$?" == "2" ]
echo "Load is HIGH! This is gooood!! $LOAD" | sed -e 's/CRITICAL/OK/'
echo "LOAD is too LOW! $LOAD" | sed -e 's/OK/CRITICAL/'
Something along those lines. The | sed -e is just doing a text replacement - OK with CRITICAL and vice versa. Good luck