Option Explicit

Public RunWhen As Double
Public Const cRunIntervalSeconds = 1 ' 1 seconds
Public Const cRunWhat = "The_Sub"  ' the name of the procedure to run

Sub StartTimer()

    RunWhen = Now + TimeSerial(0, 0, cRunIntervalSeconds)
    Application.OnTime EarliestTime:=RunWhen, Procedure:=cRunWhat, Schedule:=True
End Sub

Sub The_Sub()
Application.Cursor = xlNorthwestArrow                   'prevents mouse cusor blinking

DoEvents

With ActiveSheet
        .Cells(1, 2).Value = Format$(Now, "hh:mm:ss")
End With

DoEvents
   ' Call StartTimer to schedule the procedure again
   StartTimer
End Sub