Sorry I just realized that my phone autocorrect made that really non-sensical...
I'm not sure for what specific reason you can't do it. I seem to remember a post from at least a year ago dealing with this situation but the search function on the forum isn't working right now so I cant try to dig it up at the moment.
Generally, this is always possible to overcome by changing the logic flow of the system which it looks like you've figured out already.