Button workspace?

Alright, so I want to get crazy with my buttons, and I am pretty new to flash, so I can only do the basic animated thing.

My question lies with the fact that I kind of have to play the guessing game when making the size for my button. I know that |Modify>Document| can chance the movie proportions, but is there a way I can set a size for the |movie clip| that I am making.

I guess for an example, could I set the |button| size/workspace to be 100x30px, this way it doesn’t obstruct anything else?

Sorry, It’s a little hard to explain for me =\


The menu here, I only made the rollover box go up because if I had it go left ro right it’d go across the menuon top/under the other buttons, get what I mean?