Option Explicit
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Dim r As Range
If Not Application.Intersect(Target, Range("B:C, F:G, I:K")) Is Nothing Then
For Each r In Intersect(Target, Range("B:C, F:G, I:K"))
If Range("A" & r.Row) <> "" And r.Value = "" Then r.Value = "Unknow"
Next r
End If
End Sub