[flexcoders] How to set VBox width to a %age in actionscript

[elevight]

This is actually my second time to post this question. No one replied 
before, so maybe it got lost in the shuffle.

In MXML, I'd set the VBox width to 100% like this:

<mx:VBox width="100%"/>

But in actionscript:

var vbox:VBox = new VBox();
vbox.width = "100%";

The above won't work because the compiler will flag an error 
on "100%". Does anyone know how I can set a VBox's width as a 
percentage in actionscript?

Thanks.