Worksheet Password Protection Fails

Hello, My worksheet password protection fails after I enter data into the unprotected cells. Might it have something to do with how my VBA code is structured? I have attached my code for viewing. Thanks Everyone


Private Sub Worksheet_Change(ByVal Target As Range)

Sheets("Working Copy").Unprotect Password:="christmas"

If Intersect(Target, Union(Range("E3:E20"), Range("I3:I20"), Range("M3:M20"), Range("Q3:Q20"), Range("U3:U20"), Range("Y3:Y20"))) Is Nothing Then Exit Sub
ChangedRow = Target.Row
ChangedCol = Target.Column

Select Case Target.Value
Case 1: TextColor = 4
Case 2: TextColor = 13
Case 3: TextColor = 9
Case 4: TextColor = 5
Case 5: TextColor = 7
Case 6: TextColor = 41
Case 7: TextColor = 46
Case 8: TextColor = 12
Case Else: TextColor = 0
End Select

Target.Offset(, 2).Font.ColorIndex = TextColor
CorrespondingCol = (ChangedCol - 1) / 4 + 3
Worksheets("Finished Schedule").Cells(ChangedRow + 1, CorrespondingCol).Font.ColorIndex = TextColor

Sheets("Working Copy").Protect Password:="christmas"
End Sub