SoapUI MockService - how to use

Please excuse this newbie question, but I did not find an answer elsewhere.

I am new to SoapUI, but I have a SOAP Request problem to solve and it looks like it will work for me.

I have created a SOAP Request and sent it successfully through SoapUI.
But when I attempt to make the same Request via my application code, it fails.

Since the successful SOAP Request used all of the values from the application Request (cut & pasted), the failure must be elsewhere in the SOAP Package.

In order to check for the differences, I created a MockService from my 'real' WSDL and gave it a name:
AgentGateway.cfcSoapBinding
Now I am trying to use that MockService to 'capture' the application's Request and show the entire package to me.
I Started the MockService

But I am not sure how to modify the application code to send its request to the MockService instead of (or in addition to the 'real' web service) since I am guessing that the WSDL is the same (maybe that is a bad assumption!!).

Any assistance you might have would be greatly appreciated.

Thanks