Data Validation Combo Box - Horizontal Named List

I need to create a data validation combo box with an autofill feature. I have the following slightly modified code from the contexture website that works but only when the named lists are vertical. I need to use horizontal named lists because I have more lists than available columns in excel (350). Also I have a macro that creates the horizontal named lists automatically. I have searched multiple forums and it does not look like this issue is solved anywhere, and people just suggest that the lists are recreated vertically. Is it possible to have a data validation combo box run off of a horizontal list?

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Dim str As String
Dim cboTemp As OLEObject
Dim ws As Worksheet
Set ws = ActiveSheet
Cancel = True
Set cboTemp = ws.OLEObjects("TempCombo")
  On Error Resume Next
  With cboTemp
  'clear and hide the combo box
    .ListFillRange = ""
    .LinkedCell = ""
    .Visible = False
  End With
On Error GoTo errHandler
  If Target.Validation.Type = 3 Then
    'if the cell contains a data validation list
    Application.EnableEvents = False
    'get the data validation formula
    str = Target.Validation.Formula1
    str = Right(str, Len(str) - 1)
    With cboTemp
      'show the combobox with the list
      .Visible = True
      .Left = Target.Left
      .Top = Target.Top
      .Width = Target.Width + 5
      .Height = Target.Height + 5
      .ListFillRange = str
      .LinkedCell = Target.Address
    End With
    cboTemp.Activate
    'open the drop down list automatically
    Me.TempCombo.DropDown
End If

errHandler:
  Application.EnableEvents = True
  Exit Sub

End Sub
'=========================================
Private Sub Worksheet(ByVal Target As Range)
Dim str As String
Dim cboTemp As OLEObject
Dim ws As Worksheet
Set ws = ActiveSheet

Set cboTemp = ws.OLEObjects("TempCombo")
  On Error Resume Next
If cboTemp.Visible = True Then
  With cboTemp
    .Top = 10
    .Left = 10
    .ListFillRange = ""
    .LinkedCell = ""
    .Visible = False
    .Value = ""
  End With
End If

errHandler:
  Application.EnableEvents = True
  Exit Sub

End Sub
'====================================
'Optional code to move to next cell if Tab or Enter are pressed
'from code by Ted Lanham
Private Sub TempCombo_KeyDown(ByVal _
        KeyCode As MSForms.ReturnInteger, _
        ByVal Shift As Integer)
    Select Case KeyCode
        Case 9 'Tab
            ActiveCell.Offset(0, 1).Activate
        Case 13 'Enter
            ActiveCell.Offset(1, 0).Activate
        Case Else
            'do nothing
    End Select
End Sub

I have attached the following sample file. As you can see the code runs on the vertical list (Market1) but not on the horizontal list (Market).

Thank you so much for your help!

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