Isabelle,

Vous êtes Français ?

I'll give it a try and see if there's a performance difference
between your formula and creating a macro that changes the formula in
one cell and copies it right and down.

Just so you know what I'm working with, potentially the total
number of formulas like that will likely exceed 6,000,000 ... on just
one worksheet ! And that's just modifying the formula - it takes
another 20 minutes to calculate.

Now I know how an eight core processor with hyper-threading could
be useful.

Thanks for the in-depth support.



- Ronald K.