Goals - setting a start AND end date.

The function to set goals is cool, and I started using it to set weekly targets. 
However, there is a minor flaw in the setting up of goals. 

Recently I signed up for a challenge - Hundred Days Of Running.
It started on 24 July and ends on 31 October. 

I cannot set a goal in Garmin for the challenge parameters.  

Please, either add a day count or allow for a custom time period - i.e. allow the user to set an end date.