Ajax simulating a click
<script type="text/javascript" language="javascript">
//<![CDATA[
    function FriendCenterObject() {
        var fcAction = function(actionUrl, gamerTag, responseHandler) {
            responseHandler = responseHandler || function(response) {
                if (response.status != 0) {
                    DisplayMessageDialog('Error', response.view, 'Close', null, MessageLevelType.Error);
                }
                else {
                    DisplayMessageDialog('Message', response.view, 'Close', FriendCenter.RefreshContentAction);
                }
            }
            $.post(actionUrl, { 'gamerTag': gamerTag }, responseHandler);
        };
        this.AddFriend = function(gamerTag) {
            gamerTag = $.trim(gamerTag); // trim leading and trailing whitespaces
            if (gamerTag != "") {
                fcAction('/en-US/FriendCenter/SendFriendRequest', gamerTag);
            }
            return false;
        };
        this.RefreshContentAction = function(){};
    };
    var FriendCenter = new FriendCenterObject();
//]]>
</script>

<a href="#" onclick="FriendCenter.AddFriend('mirco')">Add to Friends List</a>

jQuery("#iframeID").src = "path/to/site";

//getting the content window html tag.
var iFrame = document.getElementById("iframeID").contentWindow;
jQuery(iFrame.body).find("#someID").click();