Making up calories the following day?

Hia guys,
I'm doing the calorie counting at the moment, and aim at 1200 calories a day. As I am in my first week I am trying to be quite strict as to what I am eating, just to get myself in the habit. I have also worked out a few times and because of this, I am usually under my daily intake o 1200 by around 100 cals. I know it's not much, but I was wondering if I am -100 one day, does it average out if I go +100 on another day.

This past 2 days I have been -100 both days, and am going for a meal tonight, but don't want to go over my cals so would I be able to include the -200 in what I've got available?!

Sounds like a silly question but I might as well ask!

Thanks!