To call stored procedures on specific api calls you have to customize your Strapi app controller or service, depending on situation. There is no way to provide you a solution, because there are too many variables in this ecuation. You need to start learning Strapi, I’m not an expert either, read this about how to customize Strapi controllers or services..
For periodic calls Strapi has even cron task similar to those in Linux.
I think you should call stored procedures not in Strapi, but in your existing frontend web framework, I suspect that you use asp.net there which is way more apropriate for such jobs. I see this setup Strapi + mssql based web framework where Strapi is the place where you add and organize data, and the mssql based framework a place where you actually consume that data (and maybe, editing existing fields). Hope it make sense.