Short Question:  How can I have an auto increment field with a single letter that is static and four numbers that auto increment with each new entry?

I looked at Zoho a few years ago to replace a spreadsheet we maintain for our car inventory.  Each car is assigned a stock number that is a combination of a single letter and four numbers.  For example G1441, G1442, G1443 are stock numbers for cars bought in 2019.  Each year the next letter is used to start over the number sequence.  So the first cars purchased in 2020 will be H0001, H0002, H0003...

I could update the starting letter manually each year in the code, but the incrementing of the stock numbers is not something that I want to manage manually in a text field.  For obvious reasons, we can not have any repeats in stock numbers, so this is critically important that the system do the incrementing for us. 

This field would be the primary key/linking field between tables/forms for various tasks within the app. The stock number is our single most used field to track our cars all the way from purchase to disposition. 

Incrementing this stock number format is easy to do in Excel, but I couldn't find a way to replicate it in Zoho a few years ago.  Is this possible?  I think Zoho would do all the other things I need and I am so ready to get off an Excel spreadsheet, but I have to cross this first hurdle with the stock number.

Any help would be greatly appreciated.