You cannot just remove it. You need to replace it with a different StateListDrawable. It will be simpler to remove the button and create a new one instead.
B4X:
Dim NewButton As Button
NewButton.Initialize("event name")
Dim parent As Panel = OldButton.Parent
parent.AddView(NewButton, OldButton.Left, OldButton.Top, OldButton.Width, OldButton.Height)
OldButton.RemoveView