Login Form With Network User And Password?

Into the form named: Administratorsfrm, I added a textbox defined as usertxt and also a textbox named passwordtxt as well as a button named logincmd.

The user defined is the Network user and this is added automatically to the usertxt field everytime when I open the Administratorsfrm form. To do this I use the next code:

Private Sub Form_Open(Cancel As Integer)
Dim wshNetwork As Object 'New wshNetwork
Set wshNetwork = CreateObject("WScript.Network")
Me.Usertxt = wshNetwork.UserName
Set wshNetwork = Nothing
End Sub

I would like that the user types his/her password (Network password or Unlocking computer) and after this could Login to the database application. I mean, the user will type his password and then the event should compare the password typed with the network password or unlocking password and if this is correct should open the database application (Main Menu Form: Mainfrm)