How to create records for a many to many relationship entities?

Hi all,

I make two custom entities ATask and BError. There is a many to many relationship between these two entities. Atask entity records created in the crm but I want to create BError entity records when the responses comes for the ATask entity in a custom work flow. I use the following code

Entity EntityA = new Entity(EntityName.NToNRelationShipBWATaskAndBError);
EntityA[NToNRelationShipBWListAndListError_Attributes.ListErrorID] = BErrorId;
EntityA[NToNRelationShipBWListAndListError_Attributes.ListErrorID] = ATaskId;
service.Create(EntityA);

but it is giving me this error.

The 'Create' method does not support entities of type 'NToNRelationShipBWATaskAndBError'.

How can I create this record for maintaining many to many relationship?

Thank You