How to create a dynamic line graph with pre populated x and not y axis data

I'm trying to create a dynamic line graph in 2010. My x axis are dates, say from A1:A200. I have corresponding data for y values, say in B1:100. My issue is that if I have my series ranges be A1:A10000,B1:B10000, the graph will automatically populate the y axis because there is data in A101:200. The trouble is, there is no data in B101:B200. I want the graph to only display the range for which there is data in A & B, but for the series to extend very far so that in the future as data is added to the B column the graph with automatically update. I want to avoid having empty cells read as zeros and flatlining unpopulated B cells. Any ideas?

Use this formula "=$B$1:INDEX($B:$B,COUNT($B:$B))" in "Name Manager".

Regards,
srikanth