Adding a field to a received Message?

Question

I am trying to learn about MSMQ at the moment. Messaging systems are pretty intriguing to me and I am working on a loan broker system I found in a book.

In that system, I have to use a mix of Web Services, Message Services and Asynchronous code to achieve a loan broker service.

Just to give you an overview, it looks like this:

The part that I am at, is the "Get Credit Score" part. The Credit Bureau takes a string of an SSN (XXXXXX-XXXX format) and returns a random credit score. The SSN is irrelevant as it just returns a random double regardless of if you use the same SSN. Just so you know.

When I receive my object from "Loan Request", it's a LoanRequest object that looks like this:

namespace LoanBroker
{
[Serializable]
 public   class LoanRequest
    {
        public string SSN { get; set; }

        public double amount { get; set; }

        public DateTime loanDuration { get; set; }
    }
}

I then use the following method to ask for a LoanQuote (not important as such yet, as I am nowhere near the part where I have to send a response from the "banks").

public LoanQuote getLoanQuote(string SSN, double amount, DateTime loanDuration)
{
    var loanrequest = new LoanRequest();
    loanrequest.SSN = SSN;
    loanrequest.amount = amount;
    loanrequest.loanDuration = loanDuration;
    Message loanMessage = new Message();
    loanMessage.Body = loanrequest;
    requestQueue.Send(loanMessage);
    var replyMessage = quoteQueue.Receive();


    return replyMessage.Body as LoanQuote;

}

So now, I send this message (loanMessage.Body = loanrequest) and then I have to use my Get Credit Score service, to receive a credit score. So far so good.

Now here is my actual question: How do I, when I have retrieved my credit score from the credit bureau, take that number and add to the message that I received, so that I can send it to the next part of the system?