给你下文吧：
UNLESS :
Not unless you offer good security.
PROVIDED:
（意味着 Yes,of course）Provided you offer good security.
注意：如果你要用 unless 前面非有 not 不可,明白吗?
More context for you,hope it helps:
Can I lend/use your computer?
A:Provided you don't damage it.
B:Not unless you promise/swear you won't damage it.