Change On_Open macro to a cell change in a range of cells

Hi all,
Is there a way to get the following code to fire once a cell changes in a range of M10:M (if any cell changes from M10 down to "end of project" ?

Private Sub Workbook_Open()
Dim i As Long
                With Sheets("Sheet1")
i = 2:      Do Until .Range("B" & i) = "End of Project"
If .Range("C" & i) < 1 And .Range("D" & i) <> "" Then _
        .Range("E" & i) = Range("A1")
            i = i + 1:  Loop
                End With
 End Sub

Thanks everyone!
Dave