Override for when to prevent automatic backups

I integrated backupninja into an application for making backups of the databases and files. In the webinterface of the application an administrative user can configure how often and when to make those backups. It's calling the backupninja main script with -n. The problem is that I cannot disable the automatic runs of backupninja without deleting the cron job which gets replaced after an update. So I came up with the idea of implementing a check against a specific string of "when" to skip automatic backups if set. If "when" is set on nothing it falls back onto the hardcoded default of "everyday at 01. To solve this the mainscript does check if when is set to 'manual'. If so it does not start any backups automatically.