Sub crearTablasyRelacion()
Dim cadSQL As String

    'creamos una tabla de facturas
    cadSQL = "CREATE TABLE Facturas " _
    & "(IdFactura INTEGER PRIMARY KEY, " _
    & "FechaFra DATETIME, " _
    & "IdCliente INTEGER)"

    'aquí utilizamos DAO
    CurrentDb.Execute cadSQL

    'creamos una tabla de detalle de facturas y relacionamos
    'con la tabla facturas a través del campo IdFactura
    cadSQL = "CREATE TABLE DetalleFacturas " _
    & "(IdDetalle COUNTER PRIMARY KEY, " _
    & "IdFactura INTEGER, " _
    & "Cantidad INTEGER, " _
    & "Descripcion TEXT(255), " _
    & "PrecioUnitario DOUBLE, " _
    & "CONSTRAINT ClaveExtFacturas FOREIGN KEY (IdFactura) " _
    & "REFERENCES Facturas ON UPDATE CASCADE ON DELETE CASCADE)"

    'aquí utilizamos ADO
    CurrentProject.Connection.Execute cadSQL

End Sub

Si las tablas estuvieran vinculadas...

Sub crearIntegridadOtraBD(nomTabla1 As String, _
                          nomTabla2 As String, _
                          nomClaveExterna As String, _
                          nomFOREIGNKEY As String)

Dim conexion As ADODB.Connection
Dim Ruta As String
Dim cadSQL As String

    Set conexion = New ADODB.Connection

    Ruta = CurrentDb.TableDefs(nomTabla1).Connect
    Ruta = Right(Ruta, Len(Ruta) - InStr(Ruta, "="))

    conexion.Open "Provider=Microsoft.Jet.OLEDB.4.0;" & _
                  "Data Source=" & Ruta & ";"

    cadSQL = "ALTER TABLE " & nomTabla1 _
    & " ADD CONSTRAINT " & nomClaveExterna _
    & " FOREIGN KEY (" & nomFOREIGNKEY & ") " _
    & "REFERENCES " & nomTabla2 _
    & " ON UPDATE CASCADE " _
    & "ON DELETE CASCADE)"

    conexion.Execute cadSQL

    conexion.Close
    Set conexion = Nothing

End Sub