Using ActiveX to open an Excel workbook but I can't run a macro.

I am using ActiveX to open an Excel workbook. The workbook has a third-party add-in but if I try to access the add-in I get

Run-time error '1004':

Sorry, we couldn't find SNLxlAddin.xla. Is it possible it was moved, renamed or deleted?

Of course the workbook functions just fine if I open it thru Excel or double-clicking from Windows Explorer so the add-in IS there.

Is this a "path" issue that I can fix in MATLAB?

Thanks!