db.Execute "UPDATE Tabelle SET Feld1='irgendwas', Feld2='etwas anderes' WHERE" & _
  "Feld3='abcd'"

Private Sub grdDataGrid_Click()
Dim varZahl As Long
Set ado1 = New Recordset
ado1.Open "select Nr from Tabelle1 Order by Nr", db, adOpenStatic, _
  adLockOptimistic
ado1.MoveLast
varZahl = ado1.Fields(0) + 1
If MsgBox("Soll die Nr.: " & varZahl & " vergeben werden?", vbYesNo, _
  "nummerieren?") Then
adoPrimaryRS.Fields(4) = varZahl
Else
Exit Sub
End If
ado1.Update 
 
On Error GoTo RefreshErr
  Set grdDataGrid.DataSource = Nothing
  adoPrimaryRS.Requery
  Set grdDataGrid.DataSource = adoPrimaryRS
  Exit Sub
RefreshErr:
  MsgBox Err.Description
End Sub