A custom view would normally only have one layout so you would do it the same as loading any other layout:
mBase.LoadLayout("LayoutName")
I think you are suggesting that you want to load different layouts into the same custom view dependant on some user interaction. If that is the case, I wouldn't, as it will mean handling the events from views from multiple layouts in one class. I would create multiple custom views, then load and remove those from a panel or create a new activity for each, It really depends on what you are trying to achieve.