Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Count > 1 Then Exit Sub
If Not Intersect(Target, Range("K3", Range("K65536").End(xlUp))) Is Nothing Then
With Application
.EnableEvents = False
If Target.Value <> "" Then Target.Offset(0, 1).Value = "ok" Else Target.Offset(0, 1).Value = ""
.EnableEvents = True
End With
End If
End Sub