First of all thanks a lot for your effort to help me. - The queueing system is a non-COM service. It uses messages to signal the queue-clients for incoming data. - My invisible control is such a queue-client. - My invisible control uses events to distribute the data-values to the other controls which visualize them. It would be no problem if my invisible control wouldn't be invisible. It seems to me that there is no window created if a control is marked "invisible" (which was a little mislead to me). I tried to create a window inside my control, but this fails, too... X| So I surrender and use the other possibility. My windowless control creates a thread which captures the queue-messages and fires the events.... ...but multithreaded event-firing makes me shiver. MfG, Sebastian