error 2501 access vba - ms-access

Question

When I run this code, I get "The Open Form action was canceled" with an error code of 2501 The line it gets caught on when I debug is the DoCmd.RunSQL (Req)
Function Compare()
Dim oDB As DAO.Database
Dim oRst As DAO.Recordset
Dim nbligne As Long
Dim Req As String
Dim default As String
Dim tables As String
Dim table
Dim i As Integer
Dim champ As String
Dim j As Integer
Set oDB = CurrentDb
Set oRst = oDB.OpenRecordset("SELECT Count(*) FROM CELLCAC;")
nbligne = oRst.Fields(0).Value
Set oRs = CurrentDb.OpenRecordset("CELLCAC")
Set fs = CreateObject("Scripting.FileSystemObject")
Set fldr = fs.getfolder("C:\Users\Documents\Application\Application_vba\Delta")
Set fls = fldr.files
Set fld = CurrentDb.OpenRecordset("TABLES_A_VERIFIER_DEFAULT")
For Each fl In fls
If fl Like "*.txt" Then
source = Left(fl.Name, Len(fl.Name) - 4)
tables = source
default = "DEFAULT_" & tables
table = CurrentDb.OpenRecordset(default)
For i = 0 To table.Count - 1
champ = table(i).Name
Req = "INSERT INTO DELTA_DEFAULT(BSCNAME, CELLNAME, MO, PARAMETRE ,DEFAULT ,RESEAU)" _
& "select DISTINCT [" & tables & "]![BSCNAME], [" & tables & "]![CELLNAME],('" & tables & "'), ('" & champ & "') ,[" & default & "]![" & champ & "],[" & tables & "]![" & champ & "] " _
& " from (" & tables & ") INNER join (" & default & ") on ( " & default & ".Zone = " & tables & ".Zone ) " _
& " Where [" & default & "]![" & champ & "] <> [" & tables & "]![" & champ & "];"
DoCmd.RunSQL (Req)
Next i
End If
Next fl
End Function

Answer 1

Instead of doing : DoCmd.RunSQL (Req),
can you try : oDB.Execute (Req)
I had several issues and this helps me a lot !

Answer 2

From the first line of your req query to the second line, you need to add a space character.
I believe that currently the query will not recognise the word SELECT if it is joined to the closed bracket.
Req = "INSERT INTO DELTA_DEFAULT(BSCNAME, CELLNAME, MO, PARAMETRE,DEFAULT ,RESEAU)" _
& " select
In addition; from what I understood I would have used the VALUES clause when creating an INSERT INTO statement. Perhaps:
Req = "INSERT INTO DELTA_DEFAULT(BSCNAME, CELLNAME, MO, PARAMETRE ,DEFAULT ,RESEAU)" _
& " VALUES (select DISTINCT [" & tables & "]![BSCNAME], [" & tables & "]![CELLNAME],('" & tables & "'), ('" & champ & "') ,[" & default & "]![" & champ & "],[" & tables & "]![" & champ & "] " _
& " from (" & tables & ") INNER join (" & default & ") on ( " & default & ".Zone = " & tables & ".Zone ) " _
& " Where [" & default & "]![" & champ & "] <> [" & tables & "]![" & champ & "]);"