Exercicio 6.4

Public Class Form1
    Public Sub New()

        ' This call is required by the designer.
        InitializeComponent()

        ' Add any initialization after the InitializeComponent() call.
        Btm_geratabuada.Text = "Gera Tabuada"
        Lbl_limite.Text = "Limite do Multiplicador"
        Txt_limite.Text = ""
        Txt_resultado.Text = ""

    End Sub

    Private Sub Btm_geratabuada_Click(sender As Object, e As EventArgs) Handles Btm_geratabuada.Click

        Dim limite As Integer = Val(Txt_limite.Text)
        Dim resultado As Integer
        Dim tabuadaresposta As String = ""

        For i As Integer = 1 To limite
            For j As Integer = 1 To 10
                resultado = i * j
                tabuadaresposta = tabuadaresposta + i.ToString + " x " + j.ToString + " = " + resultado.ToString + vbCrLf
            Next
        Next
        Txt_resultado.Text = tabuadaresposta

    End Sub
End Class

....aqui funcionou que é uma beleza :)