EXCEL: How To: Pass Workbook Handle to Sub [RESOLVED - duh]

[Webtest]

Esteemed Forum Participants and Lurkers:
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Excel 2003 VBA

I must be doing something dumb here ... I can't seem to pass a workbook reference to a Subroutine ...

Sub aTest()
    Dim aBook As Workbook
    
    Set aBook = ActiveWorkbook  'Set a handle to a WorkBook
    Debug.Print aBook.Name      'Prove that we can access by handle
    Pass_Book (aBook)           '<< THIS FAILS
End Sub

Sub Pass_Book(TestBook As Workbook)
    Debug.Print TestBook.Name, TestBook.Sheets(1).Name
End Sub

I get an error when I call "Pass_Book":

Run-time error '438': Object doesn't support this property or method

Thank you for any and all comments, suggestions, and assistance.