Basic question: Creating a webservice using the webservice tool

Hello everyone,

I am trying to achieve the following:

I want to create a webservice using the webservice tool and add this webservice to our shraepoint server. The webservice should list all recent activities to a given contact person (his ID or so).

I have general knowledge about how webservices work and how to access them using sharepoint and C#-programming in visual studio.

My problem now is that I have very little knowledge on how data is accessable in SAP CRM. Can you guide me through the process of creating a webservice with the webservice tool which does the above mentioned?

Thanks in advance,

Moritz