How could I write code to say.
Dim xlApp As Excel.Application
Dim xlWorkbook As Excel.Workbook
Dim xlWorksheet As Excel.Worksheet
This might be going in the wrong direction but here's something I've used in the past..
If Workbooks.Count > 1 Then 'Or in your case = 0
'Do Something Here'
Else
'Do Something Else'
End If
That way it will tell you if you have more than one workbook open. Otherwise it sounds like you ARE looking to see if something specific is open.
Hope that helps.