Nested Forms ASP.Net: Post to another website using ASP.Net

Hello, I have a MasterPage with a Form where a ContentPlaceHolder is located - standard aspx webforms structure. I now have a WebForm that uses my MasterPage and I need to put a Form in here as well. This form will be used to POST data to an external provider. I know in ASP.NET it's not possible to have nested forms. So what's the workaround for this? Put the code in codebehind file? Use some AJAX / JQuery? Can anyone provide me with a good example please? Thanks in advance for any help. JB