UDF to capture change in cell values

What you're saying is that you only want to trigger a UDF() if a value actually changes to a different value, not if it changes to the same value.

I've never heard of a way to tell Excel to not trigger a UDF() if the new value is the same as the old value. As far as I know you have to store the old value and compare the new value to the old value.

The UDF() could be made faster by having it trigger just once for the entire 1000 rows and keep the old values in memory instead of on a worksheet. So at least it doesn't take the time to save the values to disk.

Sub Trigger(ByVal r as Range)
    Static aOldValues
    Dim aNewValues
    Dim lRow as Long, lCol as Long

    If uBound(aOldValues,1) <= 0 Then
        aOldValues = r.Value
    Else
        aNewValues = r.Value
        For lRow = 1 to r.Rows.Count
            For lCol = 1 to r.Columns.Count
                If aNewValues(lRow, lCol) <> aOldValues(lRow, lCol) Then
                    MsgBox "Success"
                    aOldValues = aNewValues
                    Exit Sub
                End If
            Next lCol
        Nes lRow
    End If
End Sub