function form_post(formname, action, usernameField, username, passwordField, password){
        var form = document.createElement("form"); 
            form.setAttribute("name", formname);             
            form.setAttribute("method", "post");                    
            form.setAttribute("action", action); 
            form.setAttribute("target", "_blank");  
                                 
            var form_username = document.createElement("input"); 
            form_username.setAttribute("type", "hidden");                                  
            form_username.setAttribute("name", usernameField);                        
            form_username.setAttribute("value", username);                        
            form.appendChild(form_username);  
            
            var form_password = document.createElement("input");  
            form_password.setAttribute("type", "hidden");                                      
            form_password.setAttribute("name", passwordField);                        
            form_password.setAttribute("value", password);   
            form.appendChild(form_password); 
                                              
            document.body.appendChild(form); 
            form.submit();
            
            //tidy up and delete the form
            form.parentNode.removeChild(form);
    }