Have you thought of replacing all your security code with just three lines of code (see demo) ? Here's the thing ... your users have already put in a username and password to get into windows .. right ? Well the system already knows who you are and remembers your login name . So instead of having the user have to type in another name and anther password just have the system validate that the Windows Login name ( i.e. the person currenlty logged in ) has their name on the "Password" sheet in column A. If there name is there then give the access to the manager section.
So , in you situation , a click on the "access to Management info" button would just run the below function "IsOnManagersList". If the function returns True then let them in .. if the function returns False then no addmitance. Boomba no second passwords or second logging in. 
SETUP
Setup of a User is simple ... find out users windows login name and put that name in Column A of the Password Sheet. Done.
Public Sub demo()
If IsOnManagersList Then
MsgBox "Access Allowed"
Else
MsgBox "Access Denied"
End If
End Sub
Private Function IsOnManagersList() As Boolean
Set UserNameRange = ThisWorkbook.Sheets("Passwords").Range("A:A")
WindowLogInName = Environ("username")
IsOnManagersList = Application.WorksheetFunction.CountIf(UserNameRange, WindowLogInName)
End Function
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