I did not have access, when I worked with OPC. But in my system there was a person who work on maintaining the OPC database and work on OPC coding. Whenever I have some requirements like this he was able to help me. I hope there should be a similar person working on your system, and he should be able to help you. And your requirement seem to a single time one and definitely you should get it if you give him the corresponding OPC application names.
But do post if you found some ways of doing it.