I have a chart with time on the horizontal axis and a year to date total on the vertical axis. there's a "budget" and a "last year" line as well as the actual data, which is entered each day.

As data is entered, a line will appear for year to date actual to compare to the budget and last year data. The problem is that the line drops to zero at the current date, because the range contains zeros. I'd like the line to just stop, as it would if the range contained empty cells. Empty cells seem to be the only ones that get ignored. I've tried putting in a null string, but that gets treated like a zero. Is there a way to tell the chart to ignore zero values?