Inserting last-updated date into Excel

A colleague just asked how to get the date that the file was last updated into a cell in Excel.  The most obvious function TODAY() doesn’t help (unless you want to disable autocalculation, and then hit f9 before you save a file).
Create this as a macro
Function moddate(myfile) As String
moddate = Format(FileDateTime(myfile), “m/d/yy h:m ampm”)
End Function
Then call it as a function in a cell - with the full path to a file in quotes
Or if you want to get the current-file name into the argument, you can use cell(“filename”,A1) to get the current file and sheet name, then use SUBSTITUTE to strip the sheet name from the text