Flex - Sending a parameter to a custom ItemRenderer?

You may want to look into ClassFactory from the Flex APIs:

This allows you to set a prototype Object with arbitrary types / values each of which will be passed to the item renderer. From the sample:

var productRenderer:ClassFactory = new ClassFactory(ProductRenderer);
productRenderer.properties = { showProductImage: true };
myList.itemRenderer = productRenderer;

The above code assumed that "ProductRenderer" has a public property called "showProductImage" which will be set with a value of "true."

Ah, so I knew about outerDocument but not parentDocument. I was able to just use parentDocument.*whatever I want from the main App and I can access it as long as it's public.

Example:

setStyle("color", (parentDocument.availableFunding >= 0) ? POSITIVE_COLOR : NEGATIVE_COLOR);

Sweet! :)