A: 

I would suggest looking into using a SOAP extension, which in my opinion is ideal for this scenario. Here are a few links that describe the process.

http://msdn.microsoft.com/en-us/magazine/cc164007.aspx

https://ebay.custhelp.com/cgi-bin/ebay.cfg/php/enduser/std_adp.php?p_faqid=350

http://www.codeproject.com/KB/webservices/efficientsoapextension.aspx

Garett
OK... One more problem. I now have a class that inherits from the class that was generated by wsdl. This class has a Login method that calls the Login method from the 'wsdl'-class. When I apply the extension to this wsdl-class, everything seems to work, but I don't want this, because this class could be regenerated when the web service changes. So now I want to apply this extension to my own class, but then the methods in the extension class are not being called... Any suggestions?
trabart
A: 

You do not have to program. You can deploy a SOAP monitoring agent at the client that logs all Web Services call. There are tools providing a GUI to inspect the messages and there are tools that run in the background and safe the messages to files.

baranco