Formula to calculate changing total

I'm some what of a novice to Excel, so my knowledge is limited.

I've created a tracker to help track how much work is outstanding on certain days. The days are split in 3 section. Green (within service level), amber (creeping out of service level) and red (out of service level). Each day i have to insert a new column in the green section (today's date) and move the last date in green into amber and the last date in amber into the red. i need a formula where i can track how much work i have in green, amber and red, and i need the formula to change as the information in green, amber and red changes.

is this possible? if so i would greatly appreciate some help.

i hope I've made myself clear.