To CREATE formulas for the specified number of periods you'd need a macro.
Though not terribly difficult, it wouldn't be trivial either

An alternative would be to have the formulas in place but wrap them in an IF
statement so that they'd return "" if the period # was greater than the
number entered by the user, like this formula for row 15, where the user's
input is in B2 and the period numbers are in column A

=if(A15$B$2,"", - your formula here - )

Any formulas for periods beyond what the user requested would APPEAR to be
blanks.




"ajmaschinot" wrote:


I want to have a user enter a number in a box and then have Excel update
results for that many rows of results automatically.

As a more concrete example, consider an Excel mortgage worksheet where the
user enters the number of years of his/her mortgage into a box and Excel then
calculates the remainder of principle for each year inbetween. So if the
user entered 15 years, e.g., then Excel would print 15 rows of calculations,
each row containing remaining principal information for that year. If the
user then changed the input to 30 years, then 30 lines of information would
be printed. (I'm not asking about the mortgage calculations; I'm just asking
how to get Excel to automatically produce a set number of lines of any output
given a user's input).

Thanks,

Aaron