If you want to do the OnTime event say at every 1/2 second interval, then change the TimeValue("00:00:01") to 1.15740740740741E-05 / 2. Divide by 10 if you want every 1/10s interval.

e.g.
[vba]Sub StartTimer()
dTime = Now + 1.15740740740741E-05 / 2
Application.OnTime dTime, "Main", , True
End Sub [/vba]

Post #17 is getting the file contents so it will only update the values if the file contents changed. Using a CRC method it is checking each character.