Thanks for reply, AnandKiran
Yes i wanted to do it through groovy. It's done now. :-)
def request = testRunner.testCase.getTestStepByName( "GetActiveVehicles - Request 1" );
//log.info request
def property = request.getProperty("request");
//log.info property
def node = new groovy.util.XmlParser(false,false).parseText(property.value);
//log.info node
//def textNodes = node["soapenv:Body"][0].children()
//log.info textNodes
def textNodes = node["soapenv:Body"]["tem:GetActiveVehicles"]["tem:OperatorId"][0].children()
log.info textNodes
// modify
textNodes.clear();
textNodes.add( "test" + System.currentTimeMillis() );
// write back to string
def writer = new java.io.StringWriter();
def printer = new groovy.util.XmlNodePrinter( new PrintWriter( writer ));
printer.print( node );
// set property
property.setValue( writer.toString() )