Private Sub Workbook_SheetActivate(ByVal Sh As Object)
    ' Bu olay, bir sayfa etkinle?tirildi?inde tetiklenir.

    ' Sadece Admin kullanıcısı de?ilse Authentication makrosunu ça?ır
    If Sh.Name <> "Login" And Environ("Username") <> "Admin" Then
        Call Authentication(Sh)
    End If
End Sub

Sub Authentication(targetSheet As Object)
    Dim username As String
    Dim password As String
    Dim allowedSheets() As String
    Dim canAccess As Boolean
    
    ' Get username and password from the input box
    username = InputBox("Username:")
    password = InputBox("Password:")
    
    ' Access control based on username and password
    Select Case username
        Case "Admin"
            If password = "admin" Then
                ' Admin user can access all pages
                MsgBox "Welcome, Admin!"
                ' You can add specific actions for Admin here
                canAccess = True
            Else
                MsgBox "Invalid password! Access denied."
            End If
        Case "User1"
            If password = "pass1" Then
                ' User1 can access Page1
                allowedSheets = Split("Page1", ",")
                canAccess = True
            Else
                MsgBox "Invalid password! Access denied."
            End If
        Case "User2"
            If password = "pass2" Then
                ' User2 can access Page1 and Page2
                allowedSheets = Split("Page1,Page2", ",")
                canAccess = True
            Else
                MsgBox "Invalid password! Access denied."
            End If
        Case Else
            MsgBox "Invalid username! Access denied."
            Sheets("Login").Activate
    End Select
    
    ' Sayfa kontrolü yapma
    If canAccess Then
        If SheetExists(targetSheet.Name) And Not IsInArray(targetSheet.Name, allowedSheets) Then
            MsgBox "Access denied. You do not have permission to access " & targetSheet.Name
            ' Kullanıcının yetkisi olmadı?ında Login sayfasına yönlendirme
            Sheets("Login").Activate
        Else
            MsgBox "Access granted to " & targetSheet.Name
        End If
    End If
End Sub

Function SheetExists(sheetName As String) As Boolean
    ' Belirtilen sayfanın var olup olmadı?ını kontrol etme fonksiyonu
    Dim ws As Worksheet
    On Error Resume Next
    Set ws = Worksheets(sheetName)
    On Error GoTo 0
    SheetExists = Not ws Is Nothing
End Function

Function IsInArray(valToBeFound As Variant, arr As Variant) As Boolean
    ' Bir de?erin dizide olup olmadı?ını kontrol etme fonksiyonu
    Dim element As Variant
    On Error Resume Next
    IsInArray = (UBound(Filter(arr, valToBeFound)) > -1)
    On Error GoTo 0
End Function