Time of Day exclusion?

[Paul Monaghan]

Every night I have a cron job doing backups that drives cpu wait above 
my threshold of 20% - I don't want to change the threshold as any time 
other than the 3 minutes of 12:00am to 12:03am more than 20% CPU wait 
would be decidedly not normal.  I've read through the documentation 
extensively and don't believe there is a way to do a time of day 
exclusion but figured I'd ask.

Is there any way for me to do a time of day exclusion or am I best to 
just use something like:

if cpu usage (wait) > 20% for 3 cycles then alert

Assuming  "set daemon 120" is one cycle the above should be 6 minutes 
which should give me buffer around my 3 minute backup.  That make 
sense?  Is that the only way to do what I'm trying to do?

Cheers,

Paul