Yes, you can do that. There is a command with which you can send any check result to Nagios. It is usually used in distributed monitoring, but can be used in other scenarios. Just respect the syntax and it should be ok:
/usr/local/nagios/libexec/eventhandlers/submit_check_result $HOSTNAME$ '$SERVICEDESC$' $SERVICESTATE$ '$OUTPUT$'
so form the terminal you could write something like this:
**/usr/local/nagios/libexec/eventhandlers/submit_check_result ***backup_server* 'backup_service' 0 'This is a fake result check just to get rid of CRITICAL'