Instance of a sub class

Dear OOPS gurus,

I am trying to instantiate a sub class and getting an error You cannot create an instance of the class "CL_DOC_CRM_ORDER_H" within

the class itself or one of its subclasses. CL_DOC_CRM_ORDER_H is sub class of CL_DOC_CRM_ORDER and when I use create object CL_DOC_CRM_ORDER_H I get above error. Any idea how to instantiate the Sub class?

Thanks

Prasad