Option Explicit
 
Declare Function GetUserName Lib "advapi32.dll" Alias "GetUserNameA" (ByVal _
  lpBuffer As String, nSize As Long) As Long
 
Public Function GetBenutzer() As String
  Dim UserName As String
  Dim Result As Long
  Dim iLen As Integer
 
  UserName = Space$(256)
  iLen = GetUserName(UserName, Len(UserName))
 
  If InStr(UserName, Chr$(0)) > 0 Then UserName = Left$(UserName, InStr( _
    UserName, Chr$(0)) - 1)
 
  GetBenutzer = UserName
End Function

Option Explicit
Private Declare Function ShellExecute Lib "shell32.dll" Alias "ShellExecuteA" ( _
  ByVal hWnd As Long, ByVal lpOperation As String, ByVal lpFile As String, _
  ByVal lpParameters As String, ByVal lpDirectory As String, ByVal nShowCmd As _
  Long) As Long
 
Private Sub Command1_Click()
  Text1.Text = GetBenutzer()
End Sub