Now I kinda figured it out. But the problem is when
selecting the disabled cell and drag outside to extend
the series, the protection is only applied to the original
one. Is there any workaround?

Sub prt()
With ActiveSheet
.Cells.Locked = False
With Range("B4")
.Value = "MyValue"
.Interior.ColorIndex = 15
.Locked = True
End With
.Protect Password:="mypassword"
End With
End Sub


SK