Put this in the worksheet's code module, which will place a reminder in the Status Bar (this avoids needing to lock/unlock the sheet in order to write the status in to cell A1).
Put this in Sheet1 code module. The macro will execute every time sheet1 is activated.
Private Sub Worksheet_Activate()
If ActiveSheet.ProtectContents then
Application.StatusBar = "This sheet is protected"
Else:
Application.StatusBar = "This sheet is unprotected"
End If
End Sub
Private Sub Worksheet_Deactivate()
Application.StatusBar = False
End Sub
To protect/unprotect the worksheet you could add this to an Insert>Module. Then attach these macros to separate command buttons, or run from the Developer>Macros ribbon.
Const myPassword as String = "password" '<-- replace "password" with your password
Sub Sht1Protect()
Sheet1.Protect myPassword
End Sub
Sub Sht1Unprotect()
Sheet1.Unprotect myPassword
End Sub
To ensure the sheet is always protected when you close the file, insert this in the Workbook code module
Private Sub Workbook_Close()
Sht1Protect
End Sub
You may need additional handling to control whether the file is saved/not saved etc.