Macros for multiple graphs

I currently have a 70 page spreadsheet with similar data that needs representing in pie chart format. All the column headers are the same and I only need 2 columns (A and T). There are however different numbers of rows. Is it possible to write a macro to detect the number of rows before it draws the relevant pie chart (I've managed the pie chart bit!!)

See attached example, same concept but cant post real data.

Cheers

Jeremy