Link Problem

Each time I open a worksheet it asks if I want to update
the file. I always say yes because I do have active
links that I want to update from. However, the sheet
also tries to update from another source that I don't
have any references to. I've used the Find function to
try and locate the file but the results are negative.
I cannot locate any reference to the file (workbook1.xls)
and I'm not sure what to try next.