summation over a subset of a period

Hello together,
I am a newbie in AIMMs and I need help for my thesis.

t is an index for the period, here t = ( 1,2,3,…,T )

1. How can i set the initial value from E(t=1) = Q
2. How can I implement the E(T+1) 
3. How do i define t=1,…,T-1

Thank you in advance

kind regards