I'm looking for a recommendation that would indicate the most
efficient techique for having two workbooks share data on a realtime
basis. One workbook (#1) would be collecting data in realtime using an
ActiveX component and would run in a separate Excel instance. The
other workbook running in a separate Excel instance would need to
fetch this data every minute on a timer. The data would be stored in a
worksheet in workbook #1. Approximately 5000 cells would need to be
referenced....mostly numeric.
The options I've derived are as follows:
1) DDE
2) COM Add-in
3) Open read-only via Excel automation
4) Open read-only using standard workbook open
5) DAO query

Any comments ?

Whoops forgot to mention these two as well:
6) ExecuteExcel4Macro technique
7) ADO Query

Anyone have a feel for which has best performance ?