I'm trying to use an array to average a row of numbers, ignore zeroes, and
display a "-" if there is a div/0 error.

Using the format =IF(ISERROR(old_formula),"",old_formula) listed in help to
hide the error message, I end up with:

=IF(ISERROR(AVERAGE(IF(b4:h4<0,b4:h4,False)))),"-",AVERAGE(IF(b4:h4<0,b4:h4,False))

But I get an error textbox saying it is an incorrectly written array. What
do I need to change to get the desired results?