how to datasink values from a dynamic response

I'm not sure if there is a way to do what you are asking with an assertion sctipt since you wont have access to testRunner. You should be able to do that with a groovy script step. Depending on how your datasink is setup you may have to disable it so it does not run after the request and log everything. Just a warning; I have not been able to test this code, but it should get you started.

//get the response as xml
def tStep = testRunner.testCase.getTestStepByName("testStepName")
def reponse =  '${testStepName#ResponseAsXml}' 
xmlHold = context.expand(response)
def holder = new XmlParser().parseText(xmlHold)
holder instanceof Node
def max = holder.TechnicalData.Tech.size()

//loop through each tech node
for(cnt=0;cnt<max;cnt++){ 
    if(holder.TechnicalData.Tech[cnt].Tech_TechCode.text() == "67"){
		tStep = testRunner.testCase.getTestStepByName("dataSink")
        def tech_value_string = (holder.TechnicalData.Tech[cnt].tech_value_string.text()
	    tStep.setPropertyValue(dataSinkTarget,tech_value_string)
	}
}