Compound Unit

Hi,

I'm developing a DataMart and I have several KPI using compund units of measure, like:

USD/Botella

Caja/Hrs

etc.

This Units of Measure does not exist in the system, but most of the numerators and denominators exist as single units of measure. What is the best practice about handling compound units of measure?, should I create them?, should I operate numerators and denominators?

thanks for the recommendations.

Mauricio.