Actually you will be far better off if you set the active menu item versus forcing a click.
C#
this.MyThemedLinkMenu.SetActiveItem(0);
or
VB.NET
Me.MyThemedLinkMenu.SetActiveItem(0)
You can also do it by item which would look something like this:
C#
this.MyThemedLinkMenu.SetActiveItem(MyThemedLinkMenu.ItemCollection["MyKey"]);
or
VB.NET
Me.MyThemedLinkMenu.SetActiveItem(MyThemedLinkMenu.ItemCollection("MyKey"))