Also see this discussion on the community:
The handful of times I've had the pleasure of dealing with this issue have be excruciatingly difficult. It's always seems like a reasonable task when you start, easy to imagine what you need and always seems relatively easy to accomplish. When you actually get in to the real work and you start realizing that something just isn't working out the way you expect. You're still in the stages of thinking just a couple of tweaks and it'll be right. The longer you work on it, the more you realize its just not going to work. Something you were expecting to take a short time, maybe an hour, ends up in a blatant hack after 3 or 4 days of messing around with it and it's still just a hack of what you were hoping to accomplish. Even funnier (a poor choice of wording), along the way, you've asked coworkers for advice and they end up wasting a ton of time because they go thru the same process.
But one day, in the next release of Creo, it will all be solved... I can't wait till I get to use Creo Next.0