onEnterFrame - processor question

How bad is it to use onEnterFrame? I made a navigation system that has to find the coordinates of the mouse. If the mouse goes over these coordinates then the menu drops down, if it goes out of the coordinates, the menu goes back up. The thing is, is that I have 7 buttons, each with their own onEnterFrame.

I don’t use the onEnterFrame all the time, just when the user mouses over a button, then then that mc will play - dropping down the menu and starting the onEnterFrame - when the user goes out of the coordinates, the mc plays again - closeing the menu and deleting the onEnterFrame.

Instead of having the 7 onEnterFrames looking for the each button coordinates, would it be better to have just one onEnterFrame, but looking for the 7 different button coordinates?

Is there a better solution than onEnterFrame? I’m just not sure how heavy this is.