Saving values (cost) from accumulator for dashboard e.g. cost yesterday

so i have managed to get as far as a working cost from pulse for economy 10 (3 offpeak times) using cron.
now i am working on setting up a dashboard.
i would ideally like to see the total cost yesterday,this month (to date) last month, etc
is there a way of taking and storing snapshot figures

one option would be to show a graph with delta and timeperiod of day and month
but is there a way i can show the current running cost for today?

the only way i can think would be to;
use the input and reset to original value
work out the cost again via accumulator
reset this accumulator at midnight
is there a way to do this e.g. cron script