detect player issueing order

[69stehend]

lets assume there is a unit with 1 ability owned by a (computer-)player, that has shared control to all human players
now every human player can use the units ability, but how can i detect which player is using the ability? GetTriggerPlayer() works neither on the event issue bein ordered, nor on the event starts effect of an abilitiy (it returns the owner of the unit)