how to stop threads ?

[SystemX]

Hi i have a thread that runs multiple times:

VB CODE

    Private Sub pstart()

        Dim i As Integer
        For i = 0 To TextBox4.Text

            pthread = New System.Threading.Thread(AddressOf check)
            pthread.Start()

        Next

    End Sub

It can be ran upto 200 times max, how would i stop this with a click of a button as "pthread.abort()" does not stop them all.

Thanks for any help