Hi Asif,
Please check this link may help for you.
Creating a portal webservice in NWDS 7.0.14
How to Create Web Service iView through Enterprise Portal 7.0 Using an iView - Portal - SCN Wiki
The above version 7.0 but same process in 7.4 also.
Portal Web Services - Portal - SAP Library
http://help.sap.com/saphelp_nw74/helpdata/en/4b/78f7042bfb41a9e10000000a421937/frameset.htm
BR,
Durga Rao.