I have a macro I want to run every time I open *any* Excel file. It
searches across all worksheets and replaces NOW() with a constant. I
saved it in my personal.xls file as Auto_Open, but when I open any file
nothing happens. (this is where I get confused)

If I then manually open my personal.xls file the macro instantly runs
on my currently open file.

How can I make it run on any file I open in my Excel without manually
opening personal.xls...