If you are explicit about what document you want to close then you need to handle an error if that document isn't open. You might also want to ensure it isn't the foreground doc. This code looks through the current docs to close a specific one only if it is not the active document.
Code:
Sub CloseADoc()
Dim aDoc As Document
For Each aDoc In Application.Documents
Debug.Print aDoc.Name
If aDoc.Name = "Document2" And ActiveWindow.Document.Name <> "Document2" Then
aDoc.Close SaveChanges:=False
Exit For
End If
Next aDoc
End Sub