Creating graphswith empty cells.

I have a data array I use to feed a chart. The chart is cumulative spending on a quarterly basis at a weekly level and it's reviewed every week.

I have one row for each week of the quarter and the values are the QTD spending upto that week. This means that I'll only fill up the array part way during the quarter. But I want to create charts where I just select the entire array including the empty cells which will be populated with data in the coming weeks.

The problem is that when I plug in the range for the line graph, the line keeps going up and then drops to zero.

I don't want it to drop. I want the chart to pick up what's there, plot a line half way through and stop. With space for the next few weeks already in the axis.

Any ideas?