From Divinity Engine Wiki
- call PartySetFlag((CHARACTERGUID)_Character, (STRING)_Flag, (INTEGER)_DialogInstance)
Sets the flag _Flag on _Character and on every other character in the same party. The _DialogInstance parameter can be examined when catching the corresponding ObjectFlagSet event, but is otherwise unused.
- If _Character is not in a party, this call does nothing.
- This call is equivalent to setting _Flag as an object flag on every character in the same party as _Character, including the triggering of ObjectFlagSet events.