You can't use a for-loop to control timing because it's gonna try to execute all that code before rendering a single frame, and if the code takes too long to execute, you'll get the dreaded 'script is taking too long' dialog.

So either onEnterFrame or setInterval is the way to go. If you post your code in which you were attempting to use setInterval, I'd be happy to help you fix it (I'd prefer to correct existing code rather than write the whole thing from scratch).