'Place this code in the User Form code section.
Option Explicit 
 
Private Sub Cancel_Click() 
    Unload Me 
End Sub 
 
Private Sub OK_Click() 
     
    Dim c As Object 
    Dim UserName As String 
    Dim Password As String 
    Dim MyError As Integer 
     
     'Assign UserName to a variable
    UserName = UserVerification.UserName.Text 
     
     'Assign Password to a variable
    Password = UserVerification.Password.Text 
     
     'Specify the sheet and range to look up the UserName
    With Sheets("UserNames").Range("A:A") 
        Set c = .Find(What:=UserName, LookIn:=xlValues, lookat:=xlWhole, MatchCase:=True) 
    End With 
     
     'If UserName cannot be found
    If c Is Nothing Then 
        MsgBox "The username you have inputted is invalid, please try again.", vbCritical, _ 
        "Incorrect UserName" 
        Exit Sub 
    End If 
     
     'If Password is correct
    If Password = Sheets("UserNames").Range(c.Address).Offset(0, 1).Text Then 
        ThisWorkbook.Unprotect Password:="Password" 
         
         'If the sheet to make visible is not in the workbook an error will occur
         'If there is no error then make that sheet visible
        On Error Resume Next 
        Sheets(Range(c.Address).Offset(0, 2).Text).Visible = True 
        MyError = Err 
        On Error GoTo 0 
        ThisWorkbook.Protect Password:="Password", Structure:=True 
         
         'If there was an error let the user know to try again.
        If MyError <> 0 Then 
            MsgBox "The sheet specified could not be shown, please contact your system " & _ 
            "administrator.", vbCritical, "Sheet Specification Error" 
            Exit Sub 
        End If 
    Else 
         
         'If the password is incorrect let the user know to try again
        MsgBox "The password you have specified is incorrect, please try again.", vbCritical, _ 
        "Incorrect Password" 
        Exit Sub 
    End If 
     
     'Dismiss the userform
    Unload Me 
     
End Sub 
 
 'Place this code in the ThisWorkbook code section.
Option Explicit 
 
Private Sub Workbook_SheetBeforeRightClick(ByVal Sh As Object, ByVal Target As Range, Cancel As Boolean) 
     
    Cancel = True 
    If ActiveSheet.Name <> "UserNames" Then 
        ThisWorkbook.Unprotect Password:="Password" 
        ActiveSheet.Visible = xlVeryHidden 
        ThisWorkbook.Protect Password:="Password", Structure:=True 
    End If 
     
End Sub