Welcome to the forum mkuznetsov1,

Try the below in the sheet 'EDP #s', the code needs to go in that sheets code window:

 
Private Sub Worksheet_Activate()
    Dim Users As String, c As Range, pass As String
    
    Users = Environ("USERNAME")
    Set c = Worksheets("AuthUsers").Range("A1:A100").Find(Users, LookIn:=xlValues, lookat:=xlWhole, MatchCase:=False)
    pass = "password"
    
    If c Is Nothing Then
        Application.DisplayAlerts = False
        On Error Resume Next
       'may already be read only
        If ThisWorkbook.Path <> vbNullString Then
            ThisWorkbook.ChangeFileAccess xlReadOnly
            Me.Protect pass
        End If
        On Error GoTo 0
        Application.DisplayAlerts = True
    Else
        Application.DisplayAlerts = False
        On Error Resume Next
       'may already be read only
        If c = Users Then Me.Unprotect pass
        On Error GoTo 0
        Application.DisplayAlerts = True
    End If
End Sub