Custom Unemployment Tax Type

Is it possible to create a custom tax type that uses the Unemployment tax rate table to calculate a company paid tax?  Specifically, I am trying to duplicate World functionality for the Rail Road Unemployment Insurance tax.  In world, this tax is using tax type X set-up in the Unemployment Tax rate table.  Can I set up a simillar tax type in E1 (9.1)?  So far my efforts have not been working.

Is it not possible to do this, or am I misisng something?

Thanks.