macro behaviour dependent from location

[whoarrior]

Hi guys,

i'm looking for a macro which does different things depending on if i'm in the arena or not.

e.g.
inside the arena -> dispel magic
anywhere else -> pom

/cast [@arena1,noexists] Prayer of Mending
/stopmacro [@arena1,noexists]
/cast [mod,@player][@party1,nodead][] Dispel Magic

Any ideas, or do i need an addon which switchs macros when entering/leaving arenas?

(: