I am charting the average of my students' fluency progress over 10 weeks. In the spreadsheet I have set up, there is a formula set up to calculate the class average in their weekly test. This is then linked to a chart which updates automatically. However, for weeks where there is no data yet (for example, we are in week 6, so weeks 7-10 have no results yet) the cell where the formula for the average is displays #DIV?0! and this value is plotted as zero on the chart. Is there any way I can leave the formula in the cell but not have the chart plot this value as zero (or anything) until there are values to be averaged?