Public Class Form1
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Threading.ThreadPool.QueueUserWorkItem(AddressOf DoWork)
    End Sub

    Sub DoWork(ByVal o)
        Do
            Threading.Thread.Sleep(1000)
            RecValori()
        Loop
    End Sub

    Private Delegate Sub DelRecVal()
    Private Sub RecValori()
        If InvokeRequired Then
            Dim d As New DelRecVal(AddressOf RecValori)
            Invoke(d)
        Else
            Me.Text = Now.ToString
        End If
    End Sub
End Class