No, if you search for "SetScriptAreaActive" in the script function list (at
http://wiki.frictionalgames.com/hpl2/amn..._functions ) you will find that it doesn't exist, which means that it must be a custom function created in the same hps file that you copied DeactivateMonster() from.
Seriously, you need to learn the basics of scripting instead of asking the forum every time things don't work out for you. YourComputer made a YouTube tutorial. Start with that. Then learn AngelScript and read about script functions on the wiki.