'Startformular:
Public Class frmStart
 
    Dim myDialog As New frmDialog
 
    Dim WithEvents btnDialog As New Button With {.Parent = Me, .Text = "Dialog"}
 
    Private Sub btnDialog_Click(ByVal sender As Object, _
        ByVal e As System.EventArgs) Handles btnDialog.Click
 
        myDialog.ShowDialog()
    End Sub
End Class
 
'Dialogformular:
Public Class frmDialog
 
    Dim tbo As New TextBox With {.Parent = Me}
 
    Private Sub frmDialog_FormClosing(ByVal sender As Object, _
        ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles _
        Me.FormClosing
 
        If e.CloseReason = CloseReason.UserClosing Then
            Me.Hide()
            e.Cancel = True
        End If
    End Sub 
End Class