Custom spreadsheet solutions which survive long after the developer has "left the scene", are often those which users accept because they discover it _ among other benefits _ makes their work quicker and easier to do. That is why the best person to develop such solutions tend to be one who works in that area, and is therefore familiar with the way the manual system operates. S/he would have an "insider's" perspective of the best way to introduce automation other users will readily adopt _ even as it solves the identified problem(s).
The intelligent use of spreadsheets, combined with the application of the 80ᚼ rule will help to achieve the foregoing and more. One does not need any expert to start doing these things today. Just take the decision to start keeping daily, accurate records and commit to analysing them. You'll be surprised to find that you will soon become much more aware of how you're doing and what aspects of your business you should focus on more to get better returns for your efforts _ and you will be able to confidently supply verifiable/authentic financial data to back up any claims you make about your business performance to bankers or prospective investors.
From this point on, I will refer to only one of the above mentioned applications, because it is my preferred work environment. That is Microsoft Excel. I believe users of other spreadsheet applications will be able to adapt whatever I say from here for use in their own peculiar environments.
You can choose to learn how to do it yourself _ or call in someone(an Excel VB Solutions Developer for instance) who knows how. Again, this would be dependent on your purpose, how proficient you are, and/or how much time you have at your disposal. Ultimately, even if someone develops a custom application for you, it should happen with YOUR guidance at every point to ensure that it does EXACTLY what you want it to do, and that you can easily _ with your developer's support/coaching _ learn how to make modifications to it in future, without needing to call back your developer.
what is a spreadsheet used for
examples of spreadsheet packages