min_example.jl

using JuMP
using Cbc
m=Model(solver = CbcSolver());
@defVar(m, 0 <= x[1:7] <= 10000, Int);
@setObjective(m, :Min, -x[1] -x[2] );
@addConstraint(m, sum(x) == 10000); # <-- so looks the macro normally used

i = "Ni63 >= 60"
y = parse(i)
y.args[1] = :(x[[3]])
y.args[3] *= 10000

eval(Expr(:macrocall,symbol("@addConstraint"),esc(m),esc(y))) # <-- how to modify the macro itself with an expression?