Professional :: Fix The Roll Over Button On Webpage?

I have a menu bar button for my website but I need to resize the object on the roll over state, so it can be seen so it needs to be much bigger the problem is, when I create the hit are it can either be the size of the small button on the up state, or the large button on the over state. The problem here is when I make the hit area Large or as large as the over state it make the hit area way past the perimeters of the up state button so you scroll anywhere near that button and it will activate to the roll over state which can be anoying. My question is how to I make the scroll area as small as the up state button and once I am on the button itself, make the scroll area as large as the over state. So I don't scroll off by mistake. is that possible without making a roll over animation on the time line its self I would want to avoid this if at all possible.