Alpha Roll Over / Out

This is probably beyond simple, but I have no experience with AS3 at all. I know exactly what I want to do in AS2. I simply want a user to roll over ObjectA and it will turn ObjectB’s alpha to 100 so it is visible, and when rolled out it will turn invisible again.

This is what I’d do in AS2:


on (rollOver) {
    ObjectB._alpha=100;
}

on (rollOut) {
    ObjectB._alpha=0;
}

Could someone please tell me what I would write to get this to happen in AS3? I understand I would need to put the script on a frame rather than on a button, but I just don’t understand what I need to write exactly.