Option Explicit
Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
On Error GoTo 10
Application.EnableEvents = False
Sh.Name = Range("A1")
Application.EnableEvents = True
Exit Sub
10 MsgBox "Bu sayfa ismi daha önce kullanılmıştır!", vbCritical
Target.ClearContents
Target.Select
Application.EnableEvents = True
End Sub