Need shipping program made

Create an app that works with our multiple retail stores POS system through API key to pull certain bits of information to calculate automatically how much inventory we need to restock our stores from our central warehouse. We would want to be able to quickly make lists and possibly even auto send these lists through email on a periodic basis. We would need the app to be able to have us set parameters on how much stock we would want to be holding at a given store based off of sales for a particular category. I.E in a certain item if our average sales in a week is 45 units, but we have 20 currently the system would tell the warehouse to send 25 units so that it would now be at 45 which would be enough to last an average week. Or if we told it to stock enough for 2 weeks and the average sales for two weeks on an item is 100 and we were down to 15 of this item it would restock 85 items to bring its total back up to 100. We would also like the app to have some other options so that we can categorize and graph items so we could see which items are not moving well in certain stores so that they can be easily detected and transferred to other stores. There is a few other parts to this software app we want developed but this is a good gist of what we need made.