I think that you will have to provide a little more detail. When you eval code, the name of a function will be specified by a symbol, which you can create using symbol(name), where name is a string. Then you have to interpolate the function name, eg
@eval $(symbol("f$k"))(x) = x + $k
should create a function depending on the value in the variable k, eg when k =
10,
f10(x) = x + 10
