Private Declare Function NetMessageBufferSend Lib "NETAPI32.DLL" (yServer As _
  Any, yToName As Byte, yFromName As Any, yMsg As Byte, ByVal lSize As Long) As _
  Long
Private Const NERR_Success As Long = 0&
 
Public Function BroadcastMessage(sToUser As String, sFromUser As String, _
  sMessage As String) As Boolean
    Dim ToName() As Byte
    Dim FromName() As Byte
    Dim Msg() As Byte
    Dim l As Long
 
    ToName = sToUser & vbNullChar
    FromName = sFromUser & vbNullChar
    Msg = sMessage & vbNullChar
 
    If NetMessageBufferSend(ByVal 0&, ToName(0), FromName(0), Msg(0), UBound( _
      Msg)) = NERR_Success Then
        BroadcastMessage = True
    End If
End Function
 
Private Sub Command1_Click()
   If (BroadcastMessage("to", "from", "msg") = False) Then MsgBox "Fehler beim" & _
     "Versenden"
End Sub