Srinivas,

I can't really provide the sample code because integrating your database with Quickbooks can be a large undertaking.  I can help with how to go about it and try to anwer any questions you have along the way.

If you have a web application that is storing information into a SQL2K database then you have a good start on how to set up the integration.  The best way to set that up is to build the "bridge" between your database server and QuickBooks installation.  I would go with QBPro (Insert Latest Version) but any of the instances that support the QB Web Connector (QBWC) will work.  You will then want to grab the QBWC service code from the SDK download samples and set this up in IIS so that you can access the web service from you QB installation.  Once the web service is set up in IIS, you register it with the QBWC and set the frequency interval on which to call the service.  This is done on the QB Server.  I would suggest settig it up and getting it execution "as is" to test things out.

After that you want to set up how the integration between the QB Server and your SQL2K database.  You do this by implementing the methods of the QBWC service to request information from and send information to QB.  See the other comment for more indepth on implementing the QB Web Service.  That implementation will be entirely up to your custom needs and will be the most "work".  Reference the Unified Onscreen Reference that comes with the SDK to see exactly how to pass XML and the request objects.  As well as referring to the SDK manual.  It has a great step by step for getting the QB Web Service set up.

Good Luck!  Post your progress here as well.  It takes some time to tackle the learning curve of the QBSDK but once you get it and get the foundation built you can do some really cool things.

Also, eGroup provides consulting services for businesses if your company needs it.  We can help get the project off the ground and work with you to get acquainted with the SDK faster.