Propagate Windchill's part structure usage attributes 'Unit' and 'Quantity' via Creo parameters

Creo Version: 9.0.2.0

Windchill Version: 12.0.2.7

On the Uses tab of Windchill's part structure browser usually the Unit is set to 'each' by default and the Quantity shows the number of parts on the direct sub-level of the selected part. 

I want to be able to change the Unit to e.g. meters or liters via a Creo Parametric parameter. So this parameter would be defined on the component level of the assembly and then be passed to the WTPart by defining global attributes on both EPMDocument and WTPart. I also want to propagate the Quantity variable manually via a Creo parameter. 

How would I do this?