How to fix error UndefVarError when eval using?

I have some string with function (curve_expr). I need to give another name to this function and then use find_zero for my model. Unfortunatelly, I got the error: UndefVarError(:find_zero).
Here are the code:

curve_name = Symbol(:f,i,j)
@eval $curve_name(w::Any) = $curve_expr
w_new = find_zero(eval(curve_name), w0)

Thanks for answering.