Macro throwing error at protect - vba

Question

I'm trying to get a macro to operate by calling out another macro to unlock a worksheet to allow a RFID reader to scan and input data and then protect the document again to allow it from being edited.
Private Sub Worksheet_Change(ByVal Target As Range)
' call another macro
Call UnProtect
' End Sub
' Dim i As Integer
' MsgBox (Target.Row & ":" & Target.Column)
' For i = 8 To 200
If Target.Column = 3 And Target.Row <= 12 Then
If Cells(Target.Row, Target.Column).Value <> "" And Cells(Target.Row, "E").Value = "" Then
' Cells(Target.Row, "E").Value = Now()
' Cells(Target.Row, "E").NumberFormat = "h:mm AM/PM"
End If
End If
' Next
' Range("E:E").EntireColumn.AutoFit
' End Sub
' Private Sub Worksheet_Change(ByVal Target As Range)
' Dim i As Integer
' MsgBox (Target.Row & ":" & Target.Column)
' For i = 8 To 200
If Target.Column = 1 And Target.Row <= 17 Then
If Cells(Target.Row, Target.Column).Value <> "" And Cells(Target.Row, "B").Value = "" Then
Cells(Target.Row, "B").Value = Now()
' Cells(Target.Row, "F").NumberFormat = "h:mm AM/PM"
End If
End If
' Next
' Range("F:F").EntireColumn.AutoFit
' End Sub
' Private Sub Worksheet_Change(ByVal Target As Range)
' Dim i As Integer
' MsgBox (Target.Row & ":" & Target.Column)
' For i = 8 To 200
If Target.Column = 3 And Target.Row >= 15 Then
If Cells(Target.Row, Target.Column).Value <> "" And Cells(Target.Row, "D").Value = "" Then
Cells(Target.Row, "D").Value = Now()
Cells(Target.Row, "D").NumberFormat = "mm/dd/yyy"
End If
End If
' Next
Range("D:D").EntireColumn.AutoFit
' End Sub
' call another macro
Call Protect
End Sub
The two macros it is calling to are
Sub UnProtect()
'Unprotect a worksheet
Sheets("Sign in Sheet").UnProtect
End Sub
and
Sub Protect()
'Protect a worksheet
Sheets("Sign in Sheet").Protect
End Sub
However, when I only include the unlock macro, the code will work fine. But when I add the protect macro, an error code will come up
Run-Time Error '1004':
Unable to set the NumberFormat property of the Range class
and it points to
Cells(Target.Row, "D").NumberFormat = "mm/dd/yyyy"
Any ideas as to what exactly is happening.

Answer 1

I see no provision for a case when Target is more than a single cell and there's a pretty good chance that the Worksheet_Change is trying to run on top of itself.
Cycle through each range object in Target and disable event triggers.
Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
On Error GoTo safe_exit
Application.EnableEvents = False
Call Unprotect
Dim t As Range
If Not Intersect(Target, Range("A1:A17")) Is Nothing Then
For Each t In Intersect(Target, Range("A1:A17"))
If t.Value <> vbNullString And t.Offset(0, 1).Value <> vbNullString Then
t.Offset(0, 1) = Now
t.Offset(0, 1).NumberFormat = "h:mm AM/PM"
End If
Next t
End If
If Not Intersect(Target, Range("C1:C12")) Is Nothing Then
For Each t In Intersect(Target, Range("C1:C12"))
If t.Value <> vbNullString And t.Offset(0, 2).Value <> vbNullString Then
t.Offset(0, 2) = Now
t.Offset(0, 2).NumberFormat = "h:mm AM/PM"
End If
Next t
'I don't understand why column F comes into play here
' Range("F:F").EntireColumn.AutoFit
End If
If Not Intersect(Target, Range("C15:C999999")) Is Nothing Then
For Each t In Intersect(Target, Range("C15:C999999"))
If t.Value <> vbNullString And t.Offset(0, 1).Value <> vbNullString Then
t.Offset(0, 1) = Now
t.Offset(0, 1).NumberFormat = "mm/dd/yyy"
End If
Next t
Range("D:D").EntireColumn.AutoFit
End If
Call Protect
safe_exit:
Application.EnableEvents = True
End Sub