Backup schedule for odd/even weeks
 

I run my backups every Sun. morning alternating between 2 drives (macbookProOdd and macbookProEven). This works very nicely except when there are 5 Sun in a month like this month. Instead of alternating, I get two backups in a row to mackbookProeven. Is there someway to get around this?

There is not. Week 4/5 are combined (and due to the limitations of what cron format supports, weeks are days 1-7, 8-14, etc).