Public Sub refresh_km()
Dim i As Integer
 
For i = 1 To Form1.Grid3.Rows
    Form1.Grid3.Row = i
    With Form1.Grid3.Recordset
        .Fields("Ende") = Val(.Fields("Start")) + Val(.Fields("km"))
        .Update
    End With
    Form1.Grid3.RowRefresh
Next i
End Sub

mit freundlichen Grüßen
Sven