When creating an Excel chart, make the range for the chart one row or column larger than the row or column containing the NL ("Rows") or NL("Columns") function and hide the extra row or column.
For some types of charts, it is easier to put some sort of dummy label and value in the hidden row or column. "Graph Anchor" is a good dummy label and zeros are good dummy values.
Most charts will not include data from hidden rows or columns.
See the sample Customer Sales reports in the Jet Report Player for examples of charts with Auto Rows and Columns.