Service Broker - How to response the message to different queue

I'm new to Service Broker

Message Type

CREATE MESSAGE TYPE [http://ssb.csharp.at/SSB_Book/c03/RequestMessage]
VALIDATION = WELL_FORMED_XML
GO

CREATE MESSAGE TYPE [http://ssb.csharp.at/SSB_Book/c03/ResponseMessage]
    VALIDATION = WELL_FORMED_XML
GO

Contract

CREATE CONTRACT [http://ssb.csharp.at/SSB_Book/c03/HelloWorldContract]
(
    [http://ssb.csharp.at/SSB_Book/c03/RequestMessage] SENT BY INITIATOR,
    [http://ssb.csharp.at/SSB_Book/c03/ResponseMessage] SENT BY TARGET
)
GO

Queue

CREATE QUEUE InitiatorQueue
    WITH ACTIVATION
    (
        STATUS = ON,
        PROCEDURE_NAME = [ProcessResponseMessage],
        MAX_QUEUE_READERS = 1,
        EXECUTE AS SELF
    )

CREATE QUEUE TargetQueue
    WITH ACTIVATION
    (
        STATUS = ON,
        PROCEDURE_NAME = [ProcessRequestMessage],
        MAX_QUEUE_READERS = 1,
        EXECUTE AS SELF
    )

Service

CREATE SERVICE InitiatorService
ON QUEUE InitiatorQueue
(
    [http://ssb.csharp.at/SSB_Book/c03/HelloWorldContract]
)
GO

CREATE SERVICE TargetService
ON QUEUE TargetQueue
(
    [http://ssb.csharp.at/SSB_Book/c03/HelloWorldContract]
)
GO

Codes above are the example.

The question is I want to response the message to another queue(ErrorQueue for example) instead of InitiatorQueue. I've did research on Google but I can't find any resources that related to my question.

I've some idea but don't know if it's working:

1. Add another message type into Contract:
   [http://ssb.csharp.at/SSB_Book/c03/ErrorMessage] SENT BY INITIATOR
   But I don't know whether to set it as INITIATOR, TARGET or ANY
2. Create another Contract for it, if this is the solution please provide an example.
   

Thanks