Excel 2007 : RANKING TABLE #DIV/0! and #N/A

Hi i have a seriuos of sheets which rate workers performance but there two problems which i cant fix.

The first is that originaly i had the formula

=((C6+D6+E6+F6+G6)/4)/100

which was used for the not reay times average with the division amount changed by the day they worked. I then changed that to

=((C5+D5+E5+F5+G5)/COUNTIF(C5:G5,"<>0 "))/100

so that it would count these day automatically for me. but the problem then was that my tables for ranking them now does not work. and comes up with a #DIV0! error.

The second problem that i have is that some of the tables are displaying n/a when rating agetns on hang ups and long calls when they have the same amount.

is there a way round both these problems.