Scripts for beginners.

It's better to use `

GetMapDataPath()..'quest1.txt'

And even better to use something shorter (less to write, and less room for errors):

function MsgBox(text, cb)
  MessageBox(GetMapDataPath()..text..'.txt', cb);
end

MsgBox('quest1');

It's also worth figuring out more precisely whether the callback function is being called or whether it's being called but the message isn't being displayed. The console and debug messages print('bla-bla') are the primary tools for this.