Thanks Charles, I spent one day studying this weird behavior, and now I feel
better because:

1) My UDFs are calculated at every change (regardless of the current
workbook) because they refer to cells containing the volatile function
OFFSET()

2) The range referred by the OFFSET changes very seldom (it is in a hidden
sheet,) so I will make my own non volatile MyOffset that will recalculate
only when I really need it.

3) I know Excel better

4) Using IsMissing() saves 5-10% of recalculations

Thanks,
Stefano


"Charles Williams" wrote:


In the real case intead, it looks like the calculations starts in
background, the interface is responsive, and:
- If it has time to finish it runs only once;
- If it has no time to finish (because i press a key) it interrupts and
restarts.

Yes calculation restarts after an interruption (you can use VBA to mask
against an interruption).

Charles
___________________________________
The Excel Calculation Site
http://www.decisionmodels.com


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