u Can try some thing like this...
Public RunWhen As Double
Const cRunIntervalSeconds = 60
Const cRunWhat = "LockCell"
Private Sub Workbook_open()
StartTimer
End Sub
Sub StartTimer()
RunWhen = Now + TimeSerial(0, 0, cRunIntervalSeconds)
Application.OnTime EarliestTime:=RunWhen, Procedure:=cRunWhat, Schedule:=True
End Sub
Sub LockCell()
Sheets("Sheetname").Range("A1").Locked = True
StartTimer
End Sub
in the above one am running the lockcell macro after every 60 seconds...