First, thanks for the response Will.  I'll continue posting here as your
response dosn't make that seem objectionable and I see no one else posting
"off-topic" messages.  The first thing that I attempted to do was just what
you suggested - I was searching in the MSDN documentation and came across
EnableWindow() but that was not working for me.  Since this application is
not written in C so I was reluctant to discuss it too much but I guess I
described too little.

In my application I am launching a thread procudure and am then attempting
to change the enabled state of some controls on my main window (not a
dialog).  I know that on windows the state of controls is not supposed to be
altered by a separate thread.  In C# I have seen code that overcomes this
restriction but I cannot access C# code from Eiffel very easily - however I
can access C Windows API functions easily.

This is why I was hoping to use PostThreadMessage() as EnableWindow() is
doing nothing when called from my thread function.  In Eiffel I do have
access to the handles (HWND) of the controls I am using.

Do you have any ideas on how I might overcome this?

Thanks again and regards
Chris Saunders