Weight change since date feature

I have been using Cronometer for a while now, but I would like to be able to see my current diet's effects only. So for me it would be great, instead of just the 2 weeks, 4 weeks etc to be able to track my weight change from a specific date. Also to be able to flag up slip-up days so that when you look back you can see at a glance what was happening and rectify slip-up trends even if they're not obvious calorie wise..