stop certain job failing messages from appearing during a black out period or cold backup time

We are using Oracle 10.2.0.4 oem and my problem is this.

I run a cold backup oem job every night of our oracle database at 11:45 pm.  it runs around 2 hours.

I have archive log backups that run every 15 minutes, and other jobs that run fairly often against the db that send me email alerts each time they run while the backup is running.

I need a way to not run these jobs during the time the cold backup is running or if they run, don't alert me via email that they failed because I know there going to fail.

I have looked at using black outs but can't see how that will work, since I mark in the black out that I want jobs to run during the black out.  my cold backup is a job so I assume I need jobs to run during black out or it will not run.