I still don't know what you are trying to accomplish with your ev.
Assuming that you wish to create (t_4)_1 in TeX notation.. for h(r,s),
where r=t[4] and s=1..
try this
[r:?gensym(), s:?gensym(), define(h(r,s),r[s]),remvalue(r,s)];
now there is no way to "fool" h.
.......
> If you can give me a (generic!) solution with
> ?gensum()
> I will be happy to learn it.
>
> But the fact remains is that I don't see why maxima interpreter cannot
> do this for us.
(See previous note: basically because "ev" doesn't know where to get
bindings, and probably cannot do better.)
RJF