Hi All
After some R&D , i had a workaround.
Webpart on Button click
Create a blank webpart page in MOSS site , add a page viewer webpart , add your web page / ascx page into it. Code should have elements to fetch values from quesry string. In the InfoPath 2007 form add a textbox which is change to hyperlink in design mode.In any trigger event/form loading event , built the URL and set the value in the hyperlink turned textbox.
string strRequestURL = _strWebpartURL + "?strReqID=" + _strExcpRequestID;
//Set the doc URL
XPathNavigator nav = MainDataSource.CreateNavigator().SelectSingleNode("/my:myFields/<xpath of textbox", NamespaceManager);
nav.SetValue(strRequestURL);
When deployed , we can this textbox as a link.