vCAC 5.5 -- Invoking a vCO WF to dnamically populate the list of values for a service blueprint input property whose control type is Drop down list

Hi All

The use case is as follows :

I have a custom property (input parameter on service blueprint) whose control type is a Drop Down List  . If I were to have the property's attribute values dynamically populated from a vCO WF , how would I do that ?