MultiNEC can automate the repetitive steps of antenna modeling. You can start by building the model from scratch or by importing an existing model in any of several formats. Then you can run multiple test cases while letting the program make small changes to the model between runs.
MultiNEC can be used by itself if you like, but it really shines when used in conjunction with your existing antenna modeling program. MultiNEC works with EZNEC Standard, EZNEC-M Pro, EZNEC/4 Pro, NEC-Win Plus+, NEC-Win Pro, GNEC, Antenna Model (Teri Software), and 4nec2