Update:

VarIntegers did the job!

IF
MovieFinished("TACredits.bik")
THEN
ProcEnding();


// First ending

PROC
ProcEnding()
AND
CharacterGetVarInteger(CHARACTER_Player1, "EndingLive", 1)
THEN
MoviePlay(CHARACTER_Player1,"1yearlater.bik");
CharacterMakePlayer(CHARACTER_illitisPlayer);
GlobalSetEvent("DisableParty1");


// Second ending

PROC
ProcEnding()
AND
CharacterGetVarInteger(CHARACTER_Player1, "Endingdead", 1)
THEN
MoviePlay(CHARACTER_Player1,"10years.bik");
CharacterMakePlayer(CHARACTER_Elie1);
GlobalSetEvent("DisableParty2");