Glossy pixmaps

I'm looking to make borders for custom windows using pixmaps... Essentially creating a MaxGUI Window (with nothing) and a canvas on top... proceeding to draw on the canvas like so...

I don't seem to be able to google anything that will create a glossy looking border without using images... I need to be able to switch colors on the fly, so that means images will be too restricting.

you could do it with a "shine" transparent png, stick that over your drawn border and with a bit of tweaking, I reckon that would do it.