'之一
Sub Sample()
Range(  "b2" ) =   "=now()"
If Range(  "b2" ) >= Range(  "c2" )   Then
    MsgBox   "時間到"
    Exit Sub
End If
Call StartTime
End Sub

Sub StartTime()
Application.OnTime Now + TimeSerial(0, 0, 1),   "Sample"
End Sub

'之二
Sub Sample()
Do While range( "d2" ) > Now  '活動時間未過期即不斷循環
   Application.Wait Now + TimeSerial(0, 0, -1)  '控制時間
   Application.Calculate  '計算工作表
Loop
MsgBox  "時間到！"
End Sub