How to add Audience Targeting to a link at QuickLaunchBar?

I strugle a lot for setting a group to a link.So that the group users only can see the link at quicklaunchbar.
I would like to share a few lines...
if (userGroup == "Publisher")
{
node.Properties.Add("Audience", ";;;;" + groupName1);
node.Update();
}
else if (userGroup == "Certifier")
{
node.Properties.Add("Audience", ";;;;" + groupName2);
node.Update();
}