Hi,
If your xml looks like
<xml>
<quantity> 3 </quantity>
<item> Iphone 5 </item>
</xml>
def groovyUtils = new com.eviware.soapui.support.GroovyUtils( context );
def url = context.expand( '${#Project#url}' ) //define the external xml file URL
d://sample.xml in project properties
String s1= new File("${url}").text
def holder = groovyUtils.getXmlHolder(s1);
def item1 = holder.getNodeValue("//quantity")
propTestStep = context.testCase.getTestStepByName("Pro") //get the properties step name, here the property step name is Pro
propTestStep.setPropertyValue("quantity", item1)
for using this quantity in the request, simply use ${Pro#quantity} in the request