How can I draw a fieldset/groupbox container?

Hi all, first post from a long time lurker.
I hope the title makes sense, I’m using Flex and AS3. Here we go…

I’m trying to draw a surrounding box around various groups of objects (radio buttons, check boxes etc.).
Now I can pop the objects on a canvas (cnv1), which is on another canvas(baseCnv), and change the borderStyle to draw a 1px border(cnv1). I can draw a label on cnv1 over the top of the border. My problem is that labels are intrinsically transparent so the text looks crossed out. THIS IS WHERE IM AT NOW.

The next step would be to put another canvas (cnv2) the same width as the label text underneath said label, and set the background color to baseCnv Colour. My problem would then be that I can’t size cnv2 untill I know the length of the text, which I can’t find out until the field is added to cnv2 so I could count the number of letters in the string, knowing the fontSize I can work out the letters. So it is doable.

HOWEVER, this all seems a bit of a stupid way around a very simple problem. So what am I missing?
There has to be a better, more eloquent/efficient way to do this?
So what do you reckon, HOW SHOULD I DO IT?
Thanks for your patience
Michael
(AS3 & Flex noob, in case you can’t tell)