Actually, that forum doesn't include anything at all in the way of scripts for continueing onto "disc two" but it's not that hard.
Just tell the player to copy their save file into the next project. Make sure you set up a switch (preferably the first one) that switches on when you beat the previous game. Then, in the next game, make a common event that checks to make sure that switch is flipped (Make sure it's the SAME switch!) and boot them out of the game if it isn't. Also, make sure the map the save file was made on is in the next game aswell, otherwise there's a problem. Best way to set this up is to flip the switch, teleport to a designated save map (preferably, MAP001).
One thing the other topic did say, was to cut out the "New Game" feature in "Disc 2" so that they can't start on that piece. But if you don't do that, then you can use the same system to allow the player to transfer their stats to the sequal (like the PS2 .Hack games).
BTW, if you are planning on multiple "discs" for your game, make sure they have beaten all of the previous games aswell (probably using a variable instead of switches).
