Use this array* formula:

=AVERAGE(IF(A1:D1<0,A1:D1))

*An array formula has to be committed using the key combination of
Ctrl-Shift-Enter (CSE) instead of the usual Enter. If you do this
correctly then Excel will wrap curly braces { } around the formula
when viewed in the formula bar - do not type these yourself. If you
amend the formula you will need to use CSE again.

Hope this helps.

Pete

On Aug 21, 12:43*pm, Help wrote:
I'm using windows XP (older version) which does not recognize the averageif *
formula. *I need a formula that calcs the average of four different data
points some of which contain zeros. Example:

* * *A * *B * C * D * *avg
1 * 5 * *0 * 10 *15 * 10