callback to main from worker thread

Additional information: The action being performed on this control is being called from the wrong thread. You must marshal to the correct thread using Control.Invoke or Control.BeginInvoke to perform this action.

This is the error I get when I try to invoke, or callback a function that redraws a list of computers in a treeview from a worker thread.

My main thread starts several worker threads in effort to get hostnames resolved from IP addresses. There are two counters to count the number of threads and the number of threads that have returned a value. I need an example of how I can implement a sub that can be run at the completion of these threads to provide status messages and update the treeview.

Thanks in advance for your help,