Hi sriraag,
Are you saying that you want to pass a piece of XML to the web service for it to handle? If so, then I'm assuming that the web service will have some kind of "xml" parameter and that you will be passing a fragment into this parameter. To do this, follow these steps:
1. Select Tools -> Data Connections, and then click Add.
2. Select Submit, Web Service, and then type in the URL.
3. Click Next, and choose the method that you want to submit to the web service.
4. Next you will be presented with the parameters screen. For the XML parameter, choose the location of the fragment in your Main DOM and then select the option to append all children under this node.
5. Click through the rest of the wizard and you should be good to go!
6. Add a button that calls this submit data connection.
Now, we do have a web service product call Database Accelerator that takes XML as input and applies a mapping defined by the user to shred it into a relational database. There are also a slew of other features on top of this such as locking, fine-grained permissions, indexing, bulk editing, work flow, etc. If this is what your custom web service is doing, it would probably be beneficial to check out our free developer edition of DBXL to see if you can harness some of it's power in your projects. Here's the link:
http://www.qdabra.com/proddetail.asp?prod=QDBXL1
Matt Faus / Microsoft InfoPath MVPQdabra® Software / Streamline data gathering to turn process into knowledge