Change proxy server after Http Request using xNet (c#)

Question

I'm currently working on a C# Application that sends requests to a server. I am using proxies to change my IP to avoid Bans...

Issue: The only problem is it doesn't work how I want it to. I want the program to Automatically to change the username and proxy and also repeat this function (after button click:)

using xNet;

using (var request = new HttpRequest())
{
    string proxy = "127.0.0.1:8888";

    request["Accept"] = "*/*";
    request.Proxy = Socks5ProxyClient.Parse(proxy);

    var attempt = request.Post("https://fortnite-public-api.theapinetwork.com/prod09/users/id?username=" + TextBox1.Text).ToString();
}

My question for my code is: is it possible to repeat the function without using a timer? And also how can I make it so the proxy and username will automatically change after the server has responded?

How I want the code to work: Basically, the user imports a list of usernames and proxies (IP:PORT,) after the user clicks on the start button it will send the server the first line of text and will set proxy form the imported Proxy.txt file. After the server responds, it will send the server the server the second line of text and will change the proxy to the second line of proxy form the imported Text file. So it starts form ProxyCount and UserNameCount 1 and then ++ it will keep sending until it has reached the last line of the username.