check if party member in combat
 

is there no easy way to see if a party member is on any mobs hate list? like player_regen is used for your own in combat check?

You could try this :
"UNIT_COMBAT"
Fired when an npc or player participates in combat and takes damage
arg1 - the UnitID of the entity
arg2 - Action,Damage,etc (e.g. HEAL, DODGE, BLOCK, WOUND, MISS, PARRY, RESIST, ...)
arg3 - Critical/Glancing indicator (e.g. CRITICAL, CRUSHING, GLANCING)
arg4 - The numeric damage
arg5 - Damage type in numeric value (1 - physical; 2 - holy; 4 - fire; 8 - nature; 16 - frost; 32 - shadow; 64 - arcane)

Yea that will show when they are attacking or being attacked but not if they are on a hate list. a combination of that and some other events one could write something to do it and be almost 100% accurate. was hoping there was an easy way :)

Rofl, nearly everything is a combination of multiple events :D

The other option is to have it check your targets threat status with each member of your party/raid. Someone asked for something like this a few months back but can't remember if someone managed to find something that does it.

You can just poll with http://www.wowwiki.com/API_UnitAffectingCombat every so often. I don't think there's an event for it.

That event can give quite varying returns as well, so I wouldn't really call it a definitive solution by itself. You could probably combine it with some functions and events listed earlier, but determining combat for non-player units is shady business.

actually im trying to determine combat for party members.

Yes, "party members" would fall under the category of "non-player units", as the "player" unit is not considered a party member by the API.