SP2010: How to enforce unique field values for title but only for list items of particular list content types

Given a SharePoint ListA which contains ContentTypeB, ContentTypeC and ContentTypeD, I would like to enforce unique values only for title fields of ContentTypeB, but not for title fields of ContentTypeC and ContentTypeD.

That mean, when the SharePoint List allready contains Element "El1" of ContentTypeB it must not be possible to add second element "El1" of ContentTypeB, but it must be possible to add element El1 of ContentTypeC.

Unfortunately setting the EnforceUniqueValues property of Title Field of ContentType B or ContentTypeC or ContentTypeD enforce uniques values for all titles in the list, regardless of the ConetntType.