Excel Charts Member Variables

Hi Guys,
Does anyone know how I can automatically have an Excel chart adjust the number of rows being plotted on the X axis, as a function of the number of data values I import to the Excel data sheet. Sometimes I will import 100 rows from a CSV file and other times it could be 200 for instance. The data is plotted in an accompanying chart. I would like the chart to automatically adjust the source data index to the number of rows of actual data each time. I expect I will have to use a macro but don't know how to pass the row count to the appropriate chart member variable. Also, how do I count the number of rows inside the macro? Thanks for any suggestions.

ga400man please take care when posting that you use an appropriate forum.
I have moved you post to the chart forum.