If you try and open an excel file from your email and try ActiveWorkbook.Path
it will return. Also the file will be opened in Read-only mode. So you can
probably can validate these two...
C:\Documents and Settings\<username>\Local Settings\Temporary Internet Files\
If Instr(1,activeworkbook.path,"Temporary Internet Files",vbTextCompare)>0
Then
If Activeworkbook.ReadOnly = True Then
Msgbox "File opened from Email"
End If
Else
Msgbox "File residing in" & ActiveWorkbook.Path
End If
If this post helps click Yes