Endless loop with InvokeMember c#

I'm trying to mark some checkboxes and then submit a form using webbrowser, I succeeded, the problem is that my program is getting endless, It appears the form submitted, and then my form before being submitted, again submitted and again before being submitted and again...again....again.... infinitely so. I do not understand why.

I have realized that it happens in this part:

form.InvokeMember ("submit");

This is my code

private void Form1_Load(object sender, EventArgs e)
        {
            webBrowser1.Navigate("https://www.mysite.com");
        }

private void webBrowser1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
        {

            this.Text = e.Url.ToString() + " loaded";
            webBrowser1.Document.GetElementById("check1").InvokeMember("CLICK");
            webBrowser1.Document.GetElementById("check2").InvokeMember("CLICK");
            webBrowser1.Document.GetElementById("check3").InvokeMember("CLICK");
            webBrowser1.Document.GetElementById("check4").InvokeMember("CLICK");
            webBrowser1.Document.GetElementById("check5").InvokeMember("CLICK");

            foreach (HtmlElement form in webBrowser1.Document.Forms)
            {
                if (form.Name == "SearchForm")
                {
                    form.InvokeMember("submit");

                }   
            }            
        }

private void webBrowser1_Navigating(object sender, WebBrowserNavigatingEventArgs e)
        {
            this.Text = "Navigating";
        }