You can use any cell you like to record the high value, just change the sTARGET_RANGE cell to whichever cell you want to use, so if say you wanted the high value recorded in C5 you'd change the 3rd line of code to:

Const sTARGET_RANGE = "C5"

OK, to make it work:

1. Go into the VB Editor (Alt-F11)
2. In the left-hand pane double click on the sheet which is going to be updated.
3. From the left-hand drop-down list above the text editor select "Worksheet"
4. From the right-hand drop down select "Change"
5. Excel will put in the first and last lines of my code automatically, so you'll have a screen which looks like:

Private Sub Worksheet_Change(ByVal Target As Range)

End Sub

6. Paste in the code I gave you above - you won't need to paste the first and last lines, because they're already there.

7. That should be it.

Let me know if it works for you.