Private Sub ok1_Click()
On Error GoTo Err_ok1_Click

Dim file_mdb As String:           file_mdb = App.Path & "\db0.mdb"

Dim conn As ADODB.Connection:     Set conn = New ADODB.Connection
Dim rst1 As ADODB.Recordset:      Set rst1 = New ADODB.Recordset
 
conn.Provider = "Microsoft.Jet.OLEDB.4.0"
conn.Open file_mdb

rst1.Open "Таблица1", conn, adOpenDynamic, adLockOptimistic

On Error Resume Next

rst1.AddNew
rst1![pole1] = "3"      ' колонка [pole1] должна содержать только уникальные значения
rst1![pole2] = "3333"   ' и такое значение, предположим уже есть
rst1.Update

If Err.Number <>  0  Then
   Err.Clear
   rst1.CancelUpdate
End If

rst1.Close:   Set rst1 = Nothing
conn.Close:   Set conn = Nothing
  
Exit Sub

Err_ok1_Click:
     MsgBox Err.Description
     Err.Clear
End Sub