see Chip Pearson's examples at
http://www.cpearson.com/excel/TimedClose.htm

one possible solution might be to use those 2 macros (tested in Excel
2003 and they worked)

Sub delay()
runwhen = Now + TimeSerial(0, 0, 10)
Application.OnTime runwhen, "recount", , True
End Sub

Sub recount()
For i =1 to 100
Call delay
Calculate
Next i
End Sub