Can't run distinct ADODB query on open workbook? - sql

Question

I have a class ADOConnector for creating an ADODB connection to a workbook and querying the workbook:
Private objconnection As New ADODB.Connection
Sub connect(workbookPath As String)
On Error GoTo errHandler
objconnection.CommandTimeout = 99999999
objconnection.Open "Provider=Microsoft.ACE.OLEDB.12.0;" & _
"Data Source=" & workbookPath & ";" & _
"Extended Properties=""Excel 12.0 Xml;HDR=YES;IMEX=1"";"
Exit Sub
errHandler:
Err.Raise Err.Number, "ADOConnector.connect", Err.Description & _
" (" & workbookPath & ")"
End Sub
Function WorksheetQuery(selectSQL As String) As ADODB.Recordset
Dim objrecordset As New ADODB.Recordset
Const adOpenStatic = 3
Const adLockOptimistic = 3
Const adCmdText = &H1
objrecordset.Open selectSQL, _
objconnection, adOpenStatic, adLockOptimistic, adCmdText
If objrecordset.EOF Then
Set WorksheetQuery = Nothing
Exit Function
End If
Set WorksheetQuery = objrecordset
Exit Function
errHandler:
Err.Raise Err.Number, "ADOConnector.WorksheetQuery", Err.Description
Set WorksheetQuery = Nothing
End Function
I have a test method for WorksheetQuery:
Sub testADOcon()
Dim ac As New ADOConnector
Dim bkPath as string
bkPath = "U:\testFolder\testWorkbook.xlsx"
ac.connect bkPath
Dim rs As ADODB.Recordset
Set rs = ac.WorksheetQuery("select distinct * from [report$]")
End Sub
This method gives strangely inconsistent results:
If the workbook at bkPath is open, it fails with this error: The connection for viewing your linked Microsoft Excel worksheet was lost.
If the workbook at bkPath is closed, it executes successfully.
If bkPath is set as bkPath = ThisWorkbook.FullName, it executes successfully.
If the SQL is changed to "select * from [report$]", it executes successfully regardless of whether the workbook is open or closed.
How can I use distinct on another open workbook?