How to make drop menu stay down

Hello all!
Sorry if this is very basic, but not sure where else to turn.

I am a Flash beginner, my skills reach only as far as doing simple animations and editing short passages of actionscript to fit my objects.
I’ve been working on something which is my most complex project in Flash so far, but that’s not saying much.

I’m trying to create a drop down menu of sorts. The idea being when you hover over a box a rectangle drops down from behind it and on that rectangle are (text) links. I’ve created each box as a Movie Clip and the rectangle and other stuff is nested within each Movie Clip.
I’m using this (AS3) to get the rectangle to drop down:

function rectangledrop(e:MouseEvent):void {

The problem is, when I use:

function rectanglelift(e:MouseEvent):void {

the rectangle obviously disappears as soon as the pointer moves off the ‘box’. What can I do to make the rectangle stay until the mouse pointer goes off that?

Thanks for reading!