"Tushar Mehta" <tmUnderscore200310@tushar-mehta.SeeOhEm> wrote...
....
>The benefit of the approach should be obvious. The worksheet closely
>mimics the stated business problem. The formulas are simple and you
>know the results of the intermediate steps -- column of the area code
>match and the row of the phone number match, which makes debugging
>that much easier. Of course, you can also easily label the
>intermediate results by typing in text into an adjacent cell.
....

This is all very nice, but phone number lookups are ideally a database task.
The most sensible way to deal with the business problem is to use the tool
best suited to the task. The OP's task is a form of misuse of spreadsheets.

There's also the matter that the OP's phone number layout is a poor data
structure. Area codes as column headings with local phone numbers below is
much less useful than a single column of area codes and phone numbers
combined, sorted in ascending order. Phone numbers within each area code
would still be grouped, but a single fairly simple MATCH call (separately
entered area code and phone number would need to be concatenated - hopefully
you wouldn't recommend doing that alone in a separate cell) would be able to
determine whether the number exitst.

BTW, Aladin's approach is best, though I might change the custom number
format to "Y";"Y";"N".