.NET VB การส่งค่าจาก Sub form กลับมาที่ Main form ครับ

Public Class FormMain
    Public SerailID As String
    Private btnOpenForm2 As Button

    Private Form2 As Form
    Private txtSerialID As TextBox
    Private btnOK As Button


    Private Sub FormMain_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        Me.Text = "FormMain"

        btnOpenForm2 = New Button()
        btnOpenForm2.Text = "Stock Out"
        btnOpenForm2.Location = New Point(80, 80)

        Form2 = New Form()
        Form2.Text = "Form2"

        txtSerialID = New TextBox()
        txtSerialID.Location = New Point(80, 50)

        btnOK = New Button()
        btnOK.Text = "OK"
        btnOK.Location = New Point(80, 80)


        AddHandler btnOpenForm2.Click, AddressOf ButtonOpenForm_Click
        AddHandler btnOK.Click, AddressOf ButtonOK_Click


        Me.Controls.Add(btnOpenForm2)
        Form2.Controls.Add(txtSerialID)
        Form2.Controls.Add(btnOK)

    End Sub

    Private Sub ButtonOpenForm_Click()
        btnOK.DialogResult = Windows.Forms.DialogResult.OK
        txtSerialID.Text = String.Empty

        If (Form2.ShowDialog() = DialogResult.OK) Then
            MessageBox.Show(SerailID)
            'จัดการดึงข้อมูลโดยใช้ SerailID ได้เลยครับ
        End If
    End Sub

    Private Sub ButtonOK_Click()
        Me.SerailID = txtSerialID.Text
        Form2.Close()
    End Sub
End Class