Macros in an Excel workbook can be digitally “signed”. This process identifies the publisher of the macros and assures you that the code has not been altered since publication. All current versions of our Option B workbooks include a digital signature from Cornell University.
If the digital signature has expired, you are probably using an old version of the Option B application. With an expired digital signature, you cannot choose to Trust the publisher. You will have to set the Medium security setting, which is a less secure setting, for Option B to function correctly.
We recommend that you update to the current version.