Track.Height can't set $Sub() ?

I set $Sub() and Write .Height $Sub().
But, OpenBVE is not apply $Sub().
When I wrote number directly, OpenBVE is correct action.
Is it default action?

I am sorry.
I am combining two routes now.
I use $Sub(0).
This route is that $Sub(0) used for random number.
But, I am try to use $Sub(0) for Track.Ground's number.
So, $Sub(0) has been reseted.
So this is my mistake. 

... to combine two routes are very confuse...