I think he said what he meant.

he said:

if now() - timestamp(mary.xls) < 1 hour then

  run my code

else

   wait until mary.xls is less than an hour old
   run my code

end if

either way, he wants to run the code, so it can be changed to:

Do While now() - timestamp(mary.xls) > 1 hour

Loop

Run my code

You might want to put something into your loop to give an option to get out,
so that it isn't an endless loop... or you might not, depending upon what YOU
want.

You can get the timestamp of mary.xls using the FileSystemObject

Here's a sample:

Sub sbTest()

   Const cnFile = "c:\test.xls"
   
   Dim myFileTime As Date
   Dim i As Long
   
   
   myFileTime = fnFileDate(cnFile)
   MsgBox Now() - myFileTime
   Do While Now() - myFileTime > (1 / 24)
   
       i = i + 1
       If i > 10000 Then
       
           Exit Do
       
       End If
   Loop

   MsgBox "I can go!"
   

End Sub

Function fnFileDate(filename) As Date

   'dimension variables
   
   Dim fs As Object
   Dim f As Object
   
   
   'assign variables
   
   Set fs = CreateObject("Scripting.FileSystemObject")
   Set f = fs.getfile(filename)
   fnFileDate = f.DateLastModified

End Function

You'll want to take that Exit Do out and work it up a little... I just put
that in three to get myself out of the loop on the test, because my test.xls
file is 65 days old and I got into the loop!