Fit Contributor addLap timing accuracy

I have an ANT enabled device which is transmitting to an Edge device and can trigger a lap event by sending a specific ANT page.  This lap event needs to be as accurate as possible (our system can achieve millisecond level timing), and I want to record that in the fit file.  However other than calling "addLap()" in FitContributor I can't see how to achieve this.  

The ANT lap trigger page actually gets sent some time (tenths of a second) after the lap event, with a time offset inside the packet, so ideally I want to specify that the lap event ended N milliseconds ago.  Is there any way to achieve that in ConnectIQ?