Uhm... when you create the control, do something like:
PHP Code:
new myGuiControlType("foobar")
{
thiso.catchevent(this, "onMouseEnter", "onMouseEntered");
thiso.catchevent(this, "onMouseLeave", "onMouseLeft");
}
function onMouseEntered()
{
// Stuff
}
function onMouseLeft()
{
// Stuff
}