Office XP

From a macro in PowerPoint, I open an Excel file I want to work with. I use:

Excel.Workbooks.Open FileName:= _
"C:\Whatever.xls"
Excel.Application.Visible = True

Excel and the file open, but I don't have access to my Excel addins. Their
commands no longer appear in the Tools menu. (For example, Bovey's
CodeCleaner.) However, the addins show as installed and loaded.

How can I open the Excel file from PowerPoint with addins intact?

Is there anything else I should know about opening Excel from PowerPoint?

Thank you.