Feb 23, 2006 - Programmatic Skinning with Flex 2
The Drawing API allows you to create skins at runtime

From Kevin Hoyt:

"Inspired by my friend Waldo Smeet's blog entry on using 9-slice and Flash 8 to skin Flex 2 components, it occurred to me that not everybody wants to use the Flash authoring tool. In fact, Flex was created for those enterprise developers who appreciated the power of a ubiquitous runtime, but who weren't particularly interested in mastering timelines, keyframes, symbols and the myriad of other designer-oriented aspects of the authoring tool. Lucky for us, Flex 2 also includes a very impressive programmatic skinning feature. That's right, if you can draw it using the Drawing API (which I might remind you has become incredibly powerful with Flash 8), then you can use it as a skin."

Full article at:
http://weblogs.macromedia.com/khoyt/archives/2006/02/programmatic_sk.cfm