George,
Put this code in your sub: ThisWorkbook.RefreshAll (see below)
Private Sub Workbook_BeforeClose(Cancel As Boolean)
Application.OnTime dTime, "MyMacro", , False
End Sub
Private Sub Workbook_Open()
Application.OnTime Now + TimeValue("00:00:15"), "MyMacro" 'test time set
to 15 sec
End Sub
'Place the following in any Standard Module (Insert>Module)
Public dTime As Date
Sub MyMacro()
dTime = Now + TimeValue("00:00:15")
Application.OnTime dTime, "MyMacro"
ThisWorkbook.RefreshAll
MsgBox "Hooray my code works! All sheets are Refreshed"
End Sub