sci.op-research

Suppose there are some goods to be put in the storage. The quality of
them are W1~Wi (they are continuous variables). The arrive day are
D1~Di . (the are int variables and between 1 and 31). The daily output
of the storage is c(a constant). We define the total storage limit T
and the initial storage L. We want to define the constraints so that
everyday's storage is under the limit T.

My idea is to define a binary variable Yi,d to describe if a good i
arrives before day d (it can be get from Di and d),and for d=1 to
31,we calculate everyday's storage by adding Yi,d*Wi for all i and
d ,then plus L and minus d*c. At last we let it not larger than T.

But it's so complex and I believe there is some simpler way,but I
can't find it. Can anyone help me?