Public Class cls_User
    Dim _Nick As String
    Dim _chatForm As frm_chat
    .
    .
    .
 
    Sub New(ByVal Nick As String)
        _Nick = Nick
    End Sub
 
    ReadOnly Property Nick() As String
        Get
            Return _Nick
        End Get
    End Property
 
    Property chatForm() As frm_chat
        Get
            Return _chatForm
        End Get
        Set(ByVal Value As frm_chat)
            _chatForm = Value
        End Set
    End Property
 
    .
    .
    .
End Class

    Dim Users As New ArrayList
 
    Private Sub NewUser(ByVal Nick As String)
        Users.Add(New cls_User(Nick))
    End Sub

    Private Sub NewMessage(ByVal Nick As String, ByVal Message As String)
        Dim user As cls_User
        For Each user In Users
            If user.Nick = Nick Then
                If user.chatForm Is Nothing Then
                    user.chatForm = New chat_form
                    user.chatForm.show()
                End If
                user.chatForm.rtbpn.AppendText(" " & Nick & ": " & Message & _
                  vbCrLf)
            End If
        Next
    End Sub