Quote: "[quote]yes it's possible"
What a descriptive answer, you should enter that into the community guide.[/quote]
The question wasn't exactly worded the best, nor was it detailed. I think Forza correctly answered the question based on what was asked.
To answer
shadowfire's question, I guess I would need more information.
1. What do you mean by "waves"?
2. Are you talking about the player going through the same level multiple times, but with each time the player goes through there are more and more zombies, with them potentially getting tougher to kill?
3. Are you talking about creating a game where the player sequentially moves from one level to the next and the levels get increasingly difficult?
4. What is the maximum number of levels that you are looking to have the player go through before he/she wins?
5. Are you using a mod?
6. Are you familiar with scripting?