[1.9]Lock a entity on a block

Hello!

I am currently trying to make some kind of rail,but not like the minecraft basic rail,extending BlockRailBase;I want to use the onEntityColidedWithBlock method[or something alike] and a update method in my te class to expand the Block colision range;all of this making an entity like an minecart move

Also,i want my rail to be using EnumFacing , Plane.Horizontal

Now,my questions:

1:How do i lock my entity on my block to move only from a point to another

2:How do i use the update method so i detect if the state is north,to move the entity in the x axis etc.

I am curently using a Base block made by me by copying all the vanila code,then removing the enumraildirection blockstate things but the rail doesn`t get "on" my custom rail.....

1.9

P.S.:The vanilla [or forge because forge might of patched some things] code of the  BlockRailBase is confusing,or i might say it`s alike it`s class modifyer,abstract