Private Sub Worksheet_Change(ByVal Target As Range)
    If Range("A1").Value = "Car" Then
        Range("B1").Locked = False
    Else
        Range("B1").Locked = True
    End If
End Sub

Private Sub Worksheet_Change(ByVal Target As Range)
    Dim rng As Range

    Set rng = Intersect(Range("A1:A10"), Target)
    If rng Is Nothing Then
        ' Not updating the range we care about
        Exit Sub
    Else
        rng.Offset(0, 1).Locked = ... whatever ...
    End If
End Sub

Private Sub Worksheet_Change(ByVal Target As Range)

If Range("A1").Value = "Car" Then
    Range("B1").Locked = False
    Me.Unprotect ("password")
Else
    Range("B1").Locked = True
    Me.Protect ("password")
End If

End Sub