Dim myRow As Long
Public Sub EventMacro()
Dim lastRow As Long
'Clear old format
'In case of initial call, when myRow = 0
On Error Resume Next
Cells(myRow, "A").Interior.ColorIndex = xlNone
On Error GoTo 0
lastRow = Cells(Rows.Count, "A").End(xlUp).Row
Sheet1.Calculate
myRow = myRow + 1
'Setup boundary conditions
If myRow < 2 Or myRow > lastRow Then myRow = 2
Cells(myRow, 1).Interior.ColorIndex = 3 'Change this to color desired
alertTime = Now + TimeValue("00:00:05")
Application.OnTime alertTime, "EventMacro"
End Sub