Option Explicit
                
                Sub test()
                Dim conn, rs As Object, sq As String, Accounts As String
                
                Set conn = CreateObject("ADODB.Connection")
                  With conn
                    .Provider = "Microsoft.ACE.OLEDB.12.0"
                    .ConnectionString = "Data Source=" & 
                      ThisWorkbook.FullName & ";" & _
                    "Extended Properties=""Excel 12.0 
                           Xml;HDR=Yes;IMEX=1"";"
                    .Open
                      End With
                       
                           sq = "SELECT T1.[Customer Number],T1. 
                                [Customer Name],T1.[Aged Debt] " & _      
                "COUNT(T1.[Invoice Number]) as [count of Invoices] " & _ 
                                "sum(T1.[Value]) as [values] " & _
                                "FROM[Data$] T1 " & _
    "WHERE T1.[Customer Number] Not In (" & Getcust(Accounts) & ") " & _
     "GROUP BY T1.[Customer Number],T1.[Customer Name],T1.[Aged Debt]"
                                        
             Set rs = conn.Execute(sq)
                                           
              If Not rs.EOF Then
               With Me.listbox1
                .Value = ""
               .Column = rs.GetRows
              .ColumnCount = rs.Fields.Count
              .ColumnHeads = False
             .ColumnWidths = "90,90,50,50,180"
                                        End With
                                       End If
                                       
                         rs.Close
                         conn.Close
                       Set rs = npthing
                       Set conn = Nothing
                       
                       
                       End Sub
                
   
     Public Function Getcust(Accounts As String) As String
       Dim dU1 As Object, cU1 As Variant, iU1 As Long, i As Integer
                        Set dU1 = CreateObject("Scripting.Dictionary")
               cU1 = Sheets("Summary").ListObjects(1).ListColumns("Customer 
                      Number").DataBodyRange
                        For iU1 = 1 To UBound(cU1, 1)
                            dU1(cU1(iU1, 1)) = 1
                        Next iU1
                              Accounts = "'"
                        For i = 0 To dU1.Count - 1
                           Accounts = Accounts & dU1.Keys()(i) & "','"
                        Next
                          Accounts = Left(Accounts, Len(Accounts) - 5)
                          Getcust = Accounts
                          
    End Function

let
    Source = Table.NestedJoin(DataSource, {"Customer Number"}, Summary, {"ustomer Number"}, "Summary", JoinKind.LeftAnti),
    #"Grouped Rows" = Table.Group(Source, {"Customer Number", "Customer Name", "aged debt"}, {{"Count of invoices", each Table.RowCount(_), Int64.Type}, {"Value", each List.Sum([Value]), type nullable number}})
in
    #"Grouped Rows"

Sub LoadListBoxWithNotExistingCustomNo()
   Dim tbl1 As ListObject, tbl2 As ListObject, arrT1, arrT2, arrUnique, mtch, arrIt, arFin
   Dim i As Long, j As Long, dict As New Scripting.Dictionary
   Dim listB As msforms.listbox
   
   'use here the real sheets where the two involved tables exist:
   Set tbl1 = ActiveSheet.ListObjects("T1.") 'the first table Object
   Set tbl2 = ActiveSheet.ListObjects("T2.") 'the second table Object
   
   arrT1 = tbl1.DataBodyRange.Value2 'place their contents in an array for faster processing
   arrT2 = tbl2.DataBodyRange.Value2
   
   For i = 1 To UBound(arrT1)
        dict(arrT1(i, 1)) = vbNullString 'extract the unique Customers numbers
   Next i
   arrUnique = dict.keys 'place the dictionary keys in an array
   dict.RemoveAll 'empty the dictionary to reuse it...
   
   'load in the dictionary the necessary data:
   For i = 1 To UBound(arrT2)
        mtch = Application.match(arrT2(i, 1), arrUnique, True)
        If Not IsNumeric(mtch) Then
            If Not dict.Exists(arrT2(i, 1) & "|" & arrT2(i, 6)) Then
                dict.Add arrT2(i, 1) & "|" & arrT2(i, 6), Array(1, arrT2(i, 2), arrT2(i, 7))
            Else
                arrIt = dict(arrT2(i, 1) & "|" & arrT2(i, 6))   'place the item in an array
                arrIt(0) = arrIt(0) + 1 'count the number of occurrences
                arrIt(2) = arrIt(2) + arrT2(i, 7) 'add the values
                dict(arrT2(i, 1) & "|" & arrT2(i, 6)) = arrIt 'drop back the updatred ltem array
            End If
        End If
   Next i
   
   'load the final array:
   ReDim arFin(1 To dict.count, 1 To 5)
   For i = 1 To dict.count
        arFin(i, 1) = Split(dict.keys()(i - 1), "|")(0) 'the customer Number
        arFin(i, 3) = Split(dict.keys()(i - 1), "|")(1)  'the aged delay
        arFin(i, 2) = dict.Items(i - 1)(1) 'Customer name
        arFin(i, 4) = dict.Items(i - 1)(0)  'Count of Invoices
        arFin(i, 5) = dict.Items(i - 1)(2)  'Count of Invoices
   Next i
   
   Set listB = ActiveSheet.OLEObjects("ListBox1").Object: 'set the ActiveX list box
   With listB
        .ColumnCount = UBound(arFin, 2) 'set the list box number of columns
        .List = arFin 'drop the array content in the list box
   End With
End Sub

Sub LoadListBoxWithNotExistingCustomNoInSheets()
   Dim ws1 As Worksheet, ws2 As Worksheet, arrT1, arrT2, arrUnique, mtch, arrIt, arFin
   Dim i As Long, j As Long, dict As Object
   Dim listB As msforms.listbox
   
   Set ws1 = ActiveSheet 'use here the sheet you need ("My Summary Table")
   Set ws2 = ActiveSheet 'the same. I am using the same sheet because I had two tables, now transformed in ranges ("My Data source")...
   
   Dim lastR As Long
   lastR = ws1.Range("A" & ws1.rows.count).End(xlUp).row 'last row for the former first table
   arrT1 = ws1.Range("A2:E" & lastR).Value2  'place their contents in an array for faster processing
   
   lastR = ws2.Range("H" & ws2.rows.count).End(xlUp).row 'last row for the former second table (take care of the first range column TO BE USED)
   arrT2 = ws1.Range("H2:N" & lastR).Value2 'you should use your range in terms of necessary columns from second sheet ("My Data source")...
   Set dict = CreateObject("Scripting.Dictionary")
  '................
  'the existing code remains unchanged...
End Sub

Sub addScrRunTimeRef()
  'Add a reference to 'Microsoft Scripting Runtime':
  'In case of error ('Programmatic access to Visual Basic Project not trusted'):
  'Options->Trust Center->Trust Center Settings->Macro Settings->Developer Macro Settings->
  '         check "Trust access to the VBA project object model"
  Application.vbE.ActiveVBProject.References.AddFromFile "C:\Windows\SysWOW64\scrrun.dll"
End Sub