VB program - Generate n Fibonacci numbers

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim x, y, g, n, i, sum As Integer
        n = CInt(TextBox1.Text)
        x = 0
        y = 1
        TextBox2.Text = ""
        TextBox2.Text &= CStr(x) & ","
        TextBox2.Text &= CStr(y) & " "
        For i = 3 To n
            sum = x + y
            TextBox2.Text &= ", " & CStr(sum)
            x = y
            y = sum
            y = sum
        Next i
    End Sub

End Class