Backup App ONLY for external

Hey all,

I need an app that can back up one external to another external automatically - like Time Machine... just not my internal drives.

It's my work Drobo... and I just want to always have an updated version copied automatically to a second drive every night without having to manually copy things over every day.

I don't think I can tell Time Machine to ignore internal drives, can I?

Any other suggestions?

Thanks!
Brad

 

Lovely. Thank you!