Well, in this forum, I followed some guru's advice to learn coding in Python. And it surely payed off. Now, with backtrader or backtesting.py (the top two backtesting packages in python), I can tweak to test an idea within half an hour to see whether it works or not.
You will only know if the strategy is robust after a thorough backtest. Given that you are comfortable with Excel, I suggest picking up Excel VBA. It is not the most efficient programming language, but certainly one of the easiest to learn for a beginner. And since you are already doing some testing in Excel, Excel VBA would be a good start. You will most likely need to perform many backtests as you refine your strategy, explore many different measures of performance, or even test completely new strategies to augment your current one. You just don't have that flexibility if you rely on a programmer.
As you would need to backtest your trading strategy every now and then, I think you must learn to do that on your own. You will not know if the programmer is charging just for mere formality.