If accion = "new" Then
  If MessageBox.Show("¿Seguro que desea Registrar?", "Aviso Importante",
     MessageBoxButtons.YesNo, MessageBoxIcon.Question) = Windows.Forms.DialogResult.Yes Then
ClassGeneral.IURegistros("new", "0", cmbAceite.EditValue, cmbfiltro.EditValue, cmbplaca.EditValue, txtActual.EditValue, txtcambio.EditValue, dtFecha.EditValue)
  End If
End If

DialogResult.Yes

System.Windows.Forms.DialogResult.Yes