You can use OnMouseEnter and OnMouseLeave:
Sub Object_OnMouseEnter
DesktopX.Object("Target").state = "state1"
End Sub
Sub Object_OnMouseLeave
DesktopX.Object("Target").state = "Default"
End Sub
You would have to do this for each button, making sure to change "state1" to whatever state is supposed to be shown on mouse enter. "Default" state should be changed to whatever state you want showing when no buttons are moused over.
DX Scripting Reference