Excel VBA - Data connection opens workbook visibly sometimes - vba

Question

When I make a call to open a connection to another workbook, occasionally the workbook will open fully in Excel. I have ~15 data sets I pull using this method and I have not been able to identify a pattern. yesterday the refresh was quick and seamless and no workbooks visibly opened in Excel. Today 1 of 2 is opening in Excel.
Since I have users of varying experience with Excel, I would like to eliminate this possibly confusing behavior.
oCnC.Open "Provider=Microsoft.ACE.OLEDB.12.0;Mode=Read;Data Source=" & Filename & ";Extended Properties=""Excel 12.0; HDR=YES;"";"
Example code:
sub Caller
Set dTabs = New Dictionary
Set dTabs("Cerner") = New Dictionary
dTabs("Cerner")("Query") = "Select Field1, Field2 from [Sheet1$]"
dTabs("Cerner")("Hidden") = 1
Call GetMasterTables("\\\Files\File1.xlsx", dTabs)
dTabs.RemoveAll
Set dTabs = New Dictionary
Set dTabs("SER") = New Dictionary
dTabs("SER")("Query") = "Select [1],F75 from [Sheet1$]"
dTabs("SER")("Hidden") = 1
Call GetMasterTables("\\Files\File2.xlsx", dTabs)
dTabs.RemoveAll
(Cleanup)
End Sub
Private Sub GetMasterTables(Filename As String, dTabset As Dictionary, ByRef wb As Workbook)
Dim oCnC As Connection
Dim rsC As Recordset
Dim rsE As Recordset
Dim lo As ListObject
Dim rngHome As Range
Set oCnC = New Connection
Set rsC = New Recordset
Set rsE = New Recordset
Dim ws As Worksheet
oCnC.Open "Provider=Microsoft.ACE.OLEDB.12.0;Mode=Read;Data Source=" & Filename & ";" & _
"Extended Properties=""Excel 12.0; HDR=YES;"";"
rsC.ActiveConnection = oCnC
For Each i In dTabset
If SheetExists(i, wb) Then
Set ws = wb.Sheets(i)
ws.Visible = xlSheetVisible
Else
Set ws = wb.Sheets.Add(, wb.Sheets(wb.Sheets.count))
ws.Name = i
ws.Visible = xlSheetVisible
End If
Set rngHome = ws.Range("A1")
If RangeExists("Table_" & Replace(i, "-", "_"), ws) Then
Set lo = ws.ListObjects("Table_" & Replace(i, "-", "_"))
lo.DataBodyRange.Delete
Else
Set lo = ws.ListObjects.Add(, , , xlYes, rngHome)
lo.Name = "Table_" & Replace(i, "-", "_")
lo.DisplayName = "Table_" & Replace(i, "-", "_")
End If
If dTabset(i).Exists("Query") Then
rsC.Source = dTabset(i)("Query")
Else
rsC.Source = "Select * from [" & i & "$]"
End If
rsC.Open
rsC.MoveFirst
ws.Range(lo.HeaderRowRange.Offset(1, 0).address).Value = "hi"
lo.DataBodyRange.CopyFromRecordset rsC
rsC.MoveFirst
For Each j In lo.HeaderRowRange.Cells
j.Value = rsC.Fields(j.Column - 1).Name
Next j
rsC.Close
If dTabset(i).Exists("Hidden") Then
ws.Visible = xlSheetHidden
Else
ws.Visible = xlSheetVisible
End If
Next i
End Sub
Function SheetExists(ByVal shtName As String, Optional wb As Workbook) As Boolean
Dim sht As Worksheet
If wb Is Nothing Then Set wb = ActiveWorkbook
On Error Resume Next
Set sht = wb.Sheets(shtName)
On Error GoTo 0
SheetExists = Not sht Is Nothing
End Function
Function RangeExists(ByVal rngName As String, Optional ws As Worksheet) As Boolean
Dim rng As ListObject
If ws Is Nothing Then Set ws = ActiveWorksheet
On Error Resume Next
Set rng = ws.ListObjects(rngName)
On Error GoTo 0
RangeExists = Not rng Is Nothing
End Function
Update 1
Ah-ha! I have an update.
After the last test I had left the workbook open. When I came back to the computer after a few minutes there was a prompt up that the file was available for editing. Perhaps the intermittent behavior is due to the requested file being open by another user. I tested this theory by closing the workbook and then re-running the sub and it did not open the file in the app.
Update 2
Qualified my sheets references. Issue is still happening.

Answer 1

The issue is here (and anywhere else you're using Sheets without an object reference):
Set ws = Sheets(i)
ws.Visible = xlSheetVisible
Sheets is a global collection of the Application, not the Workbook that the code is running from. Track down all of these unqualified references and make them explicit:
Set ws = ThisWorkbook.Sheets(i)
You should also pass your optional parameter here:
'SheetExists(i)
'...should be...
SheetExists(i, ThisWorkbook)
I'm guessing the reason this is intermittent is that you're catching instances where the ADO connection has the other Workbook active, and your references aren't pointing to where they're supposed to.

Answer 2

In addition to the code review offered by #Comintern and #YowE3K I found a solution in the following:
Qualify my workbooks, and my sheets
Turn off screen updating (so the users can't see my magic)
Throw the book names in a dictionary before I do my update and close any extras that opened during the update.
Application.ScreenUpdating = False
For i = 1 To Application.Workbooks.count
Set dBooks(Application.Workbooks(i).Name) = i
Next i
Application.ScreenUpdating = False
Code from question
For i = 1 To Application.Workbooks.count
If dBooks.Exists(Application.Workbooks(i).Name) Then
dBooks.Remove (Application.Workbooks(i).Name)
Else
dBooks(Application.Workbooks(i).Name) = i
End If
Next i
For Each bookname In dBooks
Application.Workbooks(bookname).Close (False)
Next
Application.ScreenUpdating = True