Automatically execution of an excel macro

[fedegm]

Hi, I'm new in this forum and I need some help to solve a problem I have. I need to execute automatically a vba macro every minute. I migrate to Excel 2007 from Excel 2003. In Excel 2003 I wrote this to execute automatically the macro:

Private Sub Workbook_Open()
    Application.OnTime Now + TimeValue("00:01:00"), "actualizar_gas"
    Application.DisplayFullScreen = True
    Hoja16.Select
    Hoja16.Cells(1, 1).Select
    Range("A2").Select
    Hoja17.Select
    Hoja17.Cells(1, 1).Select
    Range("A2").Select
    Call buscar_ultimo
    Call actualizar_gas
  
End Sub


Sub actualizar_gas()
'
' Actualiza el gráfico de GAS NATURAL cada 1 minuto
'
    Time = Now + TimeValue("00:01:00")
    Application.OnTime dTime, "actualizar_gas"
    Application.ScreenUpdating = False
'
...

but in Excel 2007 is not working.
Can someone tell me what is wrong or what I have to do to solve this problem?

PD: Sorry about my english