[development] How to pass an email address vom cck to a webform

Hi On our web site we have a big number of cck nodes which do describes different classes. The students should get a chance to subscribe to a class by filling in a webform. There are a few different cck node types and a big number of cck nodes. But we'd like to use only one webform (which is a node). My question is: The CCK nodes do contain an email address. The webform should somehow get the email address of the node which linked to it (via node reference?) and send the email to this address. How can we do this. I spend several hours in searching the web and drupal.org without finding a usefull answer. I would be very happy to get some usefull information on this topic. Thanks a lot. Ernst