It is something like:

**set time /t1*t4/;**

set t(time) /t1*t3/;

Variables

A(time)

Equations

Eq1(t).. A(t+1)-A(t) =E= 1;

set t(time) /t1*t3/;

Variables

A(time)

Equations

Eq1(t).. A(t+1)-A(t) =E= 1;

it is very annoying that even though A(t4) exist, the constrains of Eq(t3) is always become:

0-A(t3) =E= 1;

How can I deal with such situation?

Please tell me the solutions of following two cases：

（1） To make Eq(t3) as "A(t4)-A(t3) =E= 1";

(2) To exclude Eq(t3);

Thank you very much for your kindly help.