Not sure what your asking can be done quite in that way. The closest I have come to simulating this is using the skill settings and the priority levels. ie
Agent 1 & Agent 2, both take the same calls.
You want Agent 1, to get the call first allowing Agent 2 more uninterupted time to do Admin work.
However if Agent 1 is busy on a call, then you need Agent 2 to pick up the next call until Agent 1 becomes available again.
By putting Agent 1 on a higher priority level, this means they will get calls 1st and only when Agent 1 is not available will Agent 2 (who you have set on a lower priority level)pick up a call.
You can then use break/lunch etc as normal and no calls will get through to that Agents line.
Note (Avaya priorety level 1 is the highest, like a ranking system)
Other than that the only option I can think of is to have Agent 2 in AUX Admin and get them to come out of it when a call queues, however this relys on keeping a close eye on the calls and may well impact your service level.