ATI Echo Enterprise Server 9.7 Scheduling Problem

I have a problem with scheduling backup jobs in ATI Echo Enterprise Server 9.7.

First I'll explain a bit how my setup is. I have 2 external USB drives for Friday backups. I need to keep 8 backups worth of Friday's. On the first drive I need to have Friday 1,3,5,7 and second drive I need to have Friday 2,4,6,8. Reason for this is each week one of the drives will be taken off site. The drive with the odd days has folders Friday1, Friday3, Friday5. Friday7 and the drive with even days has Friday2, Friday4, Friday6, Friday8

Right now I have the first 4 Friday's scheduled to run Monthly on the First, Second, Third and Fourth Friday of each month. So First Friday goes to odd days drive in folder Friday1, Second Friday goes to even days drive in Friday2 and so on.

However I've now come to a problem now, in how do I schedule Friday5 to 8. I don't see any bi-monthly option. I tried looking into weekly and it doesn't seem that would work either.

Anyone have any idea how I could get this to work?

Thanks

Oh I posted this same question back in the old support forums when they were in use, and I never got any real answer except to create 1 task have it run every 2 weeks then create a second task and have it run one week later, so my understanding is have two tasks, one that runs every 2 weeks the other every 3 weeks. However I don't see how this will resolve my problem, when asked I never got a response.