Handling Soap Exceptions?

Question

This is my problem: I am trapping all exception errors from UI which calls a web service. For example, Upon ordering of the customer, if the product selected of the user doesn't belong to the supplier then it should throw an exception error which I can trap easily if it is specified as COMexception, but it always throw a soap exception error. One solution that I try was to create an instance of an object from error message which displays the assembly name that creates the error, from that (If possible) I can trap exception errors in general. But I think I am getting far and complicated. Is there other way I can trap soapexception errors? any idea would be a great help. Thanks a lot! More power!