Timed Spawns

[xxShipxx]

I need help with triggering, i am making a Arena map, i need a trigger with a timer that spawns monster, and after they are killed it go to next round.
And there are 5 regions, wich for example spawns 2 corrupted treants in 1 region if its solo play, more 2 on the second region if are 2 players and so on.

 

[mckill2009]

check this out...