Set Height of custom component via AS3

Question

The class below is being used as a custom itemRenderer, and I want to set the height of the VBox to that of its contents (children), or perhaps the easy way would be just set it to 90%. But it must be reset each timethe dataProvider is passed to it.
public class TextDynamicLayout extends VBox
  // .. code removed for brevity
override protected function measure():void
        super.measure();
         percentHeight = 90; //this is not working as expected
         // measuredHeight = measuredMinHeight = 50;

Answer 1

I mistakenly chose "Answered." The question has not been answered completely, but I cannot undo that action of choosing "Answered."
Ben, I am not sure how that will solve the problem, could you eexplain a bit more, please?
Flex harUI, You explained the situation precisely as it is in my case. So, is there not a solution to the problem? I really need to vertically and horizontally center the VBox (with its content, and adjust the height and width of the VBox based on the text content).
Look at the image below, the VBox has the grey background and inside the VBox are dynamically rendered textFields with image bullets using the HBox . I know it is best to use the UIComponent for custom itemRenderers, but in my case, there is not really a list of items, just the one you see on Screen, only the text in the VBox changes when the dataProvider changes.
Any suggestions? Thanks.