you would want to use the SendKeys class similar to vb6. On a side note, to prevent the notorious ding you here when pressing enter, place the code in the KeyPress event and set e.Handled = true like so
Code:
    Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
        If e.KeyChar = Chr(Keys.Enter) Then
            e.Handled = True
            SendKeys.Send("{TAB}")
        End If
    End Sub