Attached is a sample that overrides the Quest typewriter text to:
1) allow the text display to be interrupted, and
2) invoke a "TypewriterDone" function when done
The sample has some large text blocks which are invoked with "test". There are three blocks, and they are shown in order, with the last repeated indefinitely.
I doubt this is the setup you want, but the overall function in the "js" attribute is what you need. The start script shows how to inject it using JS.eval, and it replaces the built-in one. So you can call the TextFX_Typewriter function as you would normally.
One thing to keep in mind is that, since the text is output one character at a time, you cannot use any HTML style tags within it, as they don't work when only partially displayed. (This is a problem with the Quest typewriter function as well, and it's not a simple problem to solve.)
Let me know if you need any changes or assistance.