Private Declare Function LogonUser Lib "Advapi32" Alias "LogonUserA" (ByVal lpszUsername As String, ByVal lpszDomain As Any, ByVal lpszPassword As String, ByVal dwLogonType As Long, ByVal dwLogonProvider As Long, phToken As Long) As Long
 
Private Const LOGON32_PROVIDER_DEFAULT    As Long = 0&
Private Const LOGON32_PROVIDER_WINNT35    As Long = 1&
Private Const LOGON32_LOGON_INTERACTIVE   As Long = 2&
Private Const LOGON32_LOGON_NETWORK       As Long = 3&
Private Const LOGON32_LOGON_BATCH         As Long = 4&
Private Const LOGON32_LOGON_SERVICE       As Long = 5&
 
Private Function Login(ByVal xi_strUserID As String, ByVal xi_strPassword As String) As Boolean
    On Error Resume Next
    Dim p_lngToken As Long
    Dim p_lngRtn As Long
   
    p_lngRtn = LogonUser(lpszUsername:=xi_strUserID, lpszDomain:=0&, lpszPassword:=xi_strPassword, dwLogonType:=LOGON32_LOGON_NETWORK, dwLogonProvider:=LOGON32_PROVIDER_DEFAULT, phToken:=p_lngToken)
                
    If p_lngRtn = 0 Then
        Login = False
    Else
        Login = True
    End If
 
    On Error GoTo 0
End Function
 
Private Sub Command1_Click()
    If Login("Benutzername", "Kennwort") Then
        MsgBox "Login korrekt"
    Else
        MsgBox "Login falsch"
    End If
End Sub