Thanks for yor answer Chris. That is exactly how I want it to work! But I'm not quite sure how to get there.

Did you answer my second or third post? What you wrote is pretty much like i wrote in my second post in which the call to SingleMeasure() resulted in the conversion error. If it was an answer to my third post, I dont know how to use it. What is iface, what does release() and Invoke really do? (I have tried to read the documentation but it goes way over my head)

Do you (or somone else) have some more code, or hints.