what do you mean by "multithreaded form" exactly?
Do you refer, for example, at the form that is shown while you copy a file,
with a progress bar, that gets upgraded while the copy is in progress?
If this is the case, you have to create a worker thread that actually
performs the lenghty operation, and periodically updates some control (e.g.
progress bar) on the form. Remember that all the updates to the UI must be
done from the main thread: you have to use somecontrol.Invoke(...) to update
the UI from the wprker thread (Invoke causes a method to be executed on the
main thread).
Hope this helps
GV