It's not a "button" but I have used a layer with a table in it. Set the
table background to be the picutre and use the OnClick event of the table -
much simpler.
You can position the layer where you want.
I have a few of these with a "sort of" rollover by creating two pictures and
using the OnMouseOver to change the back ground - or you could just change
the colour of the border, etc.etc