Option Explicit
Option Compare Text

Dim bWbProtOn As Boolean ' c

Sub twb_protect()
    ThisWorkbook.Protect Structure:=True, Windows:=False ', Password:=strPASSWORD
End Sub

Sub twb_unprotect()
    ThisWorkbook.Unprotect ' Password:=strPASSWORD
End Sub

Sub chk_twb_struct_prot_on()
Dim lShIndex&

    With ThisWorkbook
        lShIndex = .ActiveSheet.Index
        On Error Resume Next
        .Sheets.Add after:=.ActiveSheet ' c
        On Error GoTo 0
        bWbProtOn = lShIndex = .ActiveSheet.Index
        If Not bWbProtOn Then Application.DisplayAlerts = False: _
            .ActiveSheet.Delete: Application.DisplayAlerts = True
        Debug.Print bWbProtOn
    End With
End Sub

Sub test_twb_struct_prot()
    Call twb_protect
    Call chk_twb_struct_prot_on
    Call twb_unprotect
    Call chk_twb_struct_prot_on
End Sub