You can always include blank cells without affecting the result, so go way
beyond where you need, like the entire column.
=COUNTIF(H4:H65536,"<15")/COUNTIF(H4:H65536,"0")*100

"dave" wrote in message
...
I'm having a problem with a calculation, it works fine if i know what the
last cell reference is, but unforunatley this figure will vary. How can i
find out what the last cell reference is going to be ? and how do i use
that
in the calculation. Do i need to use a dummy reference ? The calculation
i'm
using is :-

(countid(h4:h38,"<15"))/(countif(h4:h39,"0"))*100.

'H39' is the cell reference that will change depending on the amount of
data
on the spreadsheet