How to delete entity link in Dynamics CRM 4 using webservices

If I have a 1:N relationship with A with B. Is there a web service method that I could use to remove the link between A and B[i] with out actually removing the entity B[i], if the Id of both are kno开发者_JS百科w. Btw A and B are custom entities. Thanks

Set the IsNull and IsNullSpecified properties of the respective lookup attribute in B[i] to true and update the record. The A record does not "know" about the link anyway.