Hello. I've made a program. The program does what it's supposed to do, for a while. The program is ment to recover my password if i loose it, but when I test it, it failes. It works fine until it comes to the number of my password.

Then this error shows: object reference not set to an instance of an object. and this section of code is highlighted:
HTML Code:
WebBrowser1.Document.GetElementById("ctl03$Login$username$input").SetAttribute("value", TextBox1.Text)
Here is my completed code:
HTML Code:
Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dialog1.ShowDialog()
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        If TextBox1.Text = "" Then
            MsgBox("Fyll inn feltene")
            Exit Sub
        ElseIf TextBox2.Text = "" Then
            MsgBox("Fyll inn feltene")
            Exit Sub
        ElseIf ComboBox2.Text = "" Then
            MsgBox("Anngi skole")
            Exit Sub
        ElseIf ComboBox1.Text = "" Then
            MsgBox("Anngi tal for andre del av passordet")
            Exit Sub
        ElseIf TextBox1.Text = "koug" Then
            MsgBox("Administrator har sperret dette fra dette programmet.")
            Exit Sub
        ElseIf TextBox1.Text = "mobe" Then
            MsgBox("Administrator har sperret dette fra dette programmet.")
            Exit Sub
        ElseIf TextBox1.Text = "wiro" Then
            MsgBox("Administrator har sperret dette fra dette programmet.")
            Exit Sub
        ElseIf TextBox1.Text = "toso" Then
            MsgBox("Administrator har sperret dette fra dette programmet.")
            Exit Sub
        ElseIf TextBox1.Text = "laor" Then
            MsgBox("Administrator har sperret dette fra dette programmet.")
            Exit Sub
        End If

        MsgBox("Ser etter passordet. Du vil bli varsla når programmet er ferdig.")

        info()

    End Sub
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'open website in wb
        Number1.Text = "0"
        number2.Text = "0"
        number3.Text = "0"

        WebBrowser1.Navigate("https://www.itslearning.com/Index.aspx?CustomerId=565&Username=")
    End Sub

    Private Sub ComboBox2_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox2.SelectedIndexChanged
        'select combobox item in webpage
        If ComboBox2.SelectedIndex <> -1 Then
            Dim element As HtmlElement = WebBrowser1.Document.GetElementById("ctl03_Login_site_input")
            Dim optionsElement As HtmlElement = element.GetElementsByTagName("option").Cast(Of HtmlElement).First(Function(el) el.InnerText = ComboBox2.Text)
            optionsElement.SetAttribute("selected", "selected")
        End If
    End Sub

    Private Sub WebBrowser1_DocumentCompleted(ByVal sender As System.Object, ByVal e As System.Windows.Forms.WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted
        'fill combobox
        If WebBrowser1.ReadyState <> WebBrowserReadyState.Complete Then Return
        Dim element As HtmlElement = WebBrowser1.Document.GetElementById("ctl03_Login_site_input")
        Dim options() As String = element.GetElementsByTagName("option").Cast(Of HtmlElement).Select(Function(el) el.InnerText).ToArray
        ComboBox2.Items.AddRange(options)
    End Sub

    Private Sub info()
        Timer1.Stop()
        Number1.Text = Number1.Text + 1
        If Number1.Text = "10" Then
            Number1.Text = "0"
            number2.Text = number2.Text + 1
        ElseIf number2.Text = "10" Then
            number2.Text = "0"
            number3.Text = number3.Text + 1
        ElseIf number3.Text = "10" Then
            number3.Text = "9"
        ElseIf number3.Text = "9" & number2.Text = "9" & Number1.Text = "9" Then
            MsgBox("Fant ikke passordet")
        End If

        Dim cur1 As String
        cur1 = number3.Text & number2.Text & Number1.Text
        Label6.Text = cur1

        WebBrowser1.Document.GetElementById("ctl03$Login$username$input").SetAttribute("value", TextBox1.Text)
        WebBrowser1.Document.GetElementById("ctl03$Login$password$input").SetAttribute("value", TextBox2.Text & cur1)
        WebBrowser1.Document.GetElementById("ctl03$Login$loginbtn").InvokeMember("click")

        Timer2.Start()
    End Sub

    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        info()
    End Sub

    Private Sub info2()
        Timer2.Stop()

        Dim cur2 As String
        cur2 = number3.Text & number2.Text & Number1.Text

        If WebBrowser1.Url.ToString = "https://www.itslearning.com/main.aspx?StartUrl=main%2fmainmenu.aspx" Then
            MsgBox("Passordet ble funnet:  " & TextBox2.Text & cur2)
            Exit Sub
        Else
            Timer1.Start()
        End If

    End Sub

    Private Sub Timer2_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer2.Tick
        info2()
    End Sub
End Class
Can someone a bit more experienced please tell me what's wrong? Thanks in advance :-)