Hi Gérard,
you have two main options....
either replace the for loop with a while loop (N needs to be determined programatically) or place the contents of the FOR loop in a case statement, leaving one case empty. By pressing a button linked to the case statement, the calculations for the remaining iterations can basically be skipped. The current iteration will still execute to completion though.....
Hope this helps
Shane.
Using LV 6.1 and 8.2.1 on W2k (SP4) and WXP (SP2)