Use exisiting bitmap button to create stretchy button?

[Black Panther]

I´am not sure if i have understand your request really good, but i have tried to edit a finished button and fill it with (carbon fiber fill) also bitmap fill, but that not work with the button, so i have drawn only lines and changed the color of the button. attached is .xar file maybe that help you if you can see it, sorry if anything wrong from me, i´am not so prof. in web things.
But want to help.
Best regards
BP