stop process with button

[calmar <mac calmar ws>]

Hi,
as far as I found out (not too much), it's possible to give a function 
(calculating function) it's own thread, so it can be cancelled when 
needed from the main progam p.e. with a 'stop' button.
Would there be also another way to stop a calculating with a button 
without threads?
(in the first instance I should try it without threads, in order it can 
run also on ms windows without crashes....)

Thanks for any ideas!

marco candrian