Looks like I wasn't being clear. There's no reason why a normal person should understand all of this mumbo-jumbo.
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My apologies. Here are the steps you should follow:
1. Exit the game (or don't start it if you're not already playing it).
2. Start Windows Notepad and find BALDUR.INI.
3. Look for the line that says [Program Options]. Right under it, add the line:
DebugMode=1
4. Save BALDUR.INI and exit Notepad.
5. Start Shadows of Amn. Load a Saved Game.
6. While you're inside the game, press the CTRL key, hold it down, and press the Space bar. A box will pop up at the bottom of your screen.
7. Type the following in the box:
CLUAConsole:SetGlobal("BKorgan18","LOCALS",1)
8. From then on, every time you press CTRL-Space in the game, "CLUAConsole" will automatically appear in the box, awaiting your commands. You can type other commands such as:
AddGold("1000")
CreateItem("SCRL75")
CreateCreature("BOO") (then you can "CTRL-Q" him and add him to your party!)
Let me clarify what happens in the game when Korgan talks to Aerie. First, the game checks the state of certain variables. If the variables permit it, the dialogue takes place. If the variables don't permit it, the dialogue doesn't take place. When Aerie threatens the leave the group, the game starts a timer. If the timer expires and the condition it checks is not met (for example, if Aerie and Korgan are both still in the group), another dialogue is triggered, and in this case, Aerie leaves the group. (I think you can find her at the Circus, but I don't think she'll rejoin you, but I'm not sure.) Once that timer starts ticking, it's too late to use SetGlobal("KorganAerieGrump","GLOBAL",0). That's why I recommend that you use SetGlobal("BKorgan18","LOCALS",1) before Aerie ever threatens to leave.