Hi,

The intention of Krishna's reply was to outline one potential approach and that you adapt it to suit your needs. Where Krishna's code shows a message box you should change that to call your macro instead.

That aside, I think you should look into using Timers. Have a look at the Application.OnTime method in your VBA helpfile. For further information and examples you can read this excellent article by Chip Pearson:
http://www.cpearson.com/excel/OnTime.aspx

For now I recommend that you avoid using the Windows Timers: unless they are used with due caution and care they may cause Excel to crash under certain circumstances.

Good luck!