Public Class Form1
    Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        t.Abort()
    End Sub

    Dim t As New Threading.Thread(AddressOf DoWork)

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        t.Start()
    End Sub


    Sub DoWork()
        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