Well. you have descrete increments that luckily correlate to the index. So if your user enters 110 you can just divide by 100 (quotient) and it will give you 1 which you can pass to the index array function to extract the row.
The fun begins when you want to get to the closest higher or lower than the value input
Naah. You only want to replace your home-grown. memory/handle hungry, local object database. We all know of a self contained, blisteringly fast, serverless RDMS that would fit the bill nicely I don't understand folks that don't use it even if it's just for error logging.