Here's some code I use in one of my oh-so-cool programs
You could also use Open File For Binary... it's faster.

Code:
'first check the filesize
If FileLen(OLDFILE) <> FileLen(NEWFILE) Then 
'= updated
'do all the things you need and
Exit Sub/Function 'to prevent it to display it's updated twice :)
End If

'Now the filechecking if the size is the same.
Open OLDFILE For Input As #1
Open NEWFILE For Input As #2
Do While Not EOF(1)
Line Input #1, tmp1
Line Input #2, tmp2
If tmp1 <> tmp2 Then '= Updated!
'Do the things you need
Exit Sub/Function
End IF
Loop

'If the code reaches here there's nothing updated!

Get the idea?

whoohee this is my 800th post