How do I use a cell on a different worksheet within the same workbook to get
the name of an external workbook that I use for the name or values of a
series in Source Data for a chart. I want to use a workbook as a template and
just change change one cell instead of all of the references to the external
workbook.

Example
=[Test_App_Data.xls]Ticket_Counts!$B$1 - I want to get the Test_App_Data.xls
from a worksheet in the current workbook

Thanks for your help