We have both Zoho Books and Zoho Inventory. We wrote a lot of customer function program on Zoho Books on Invoice and Purchase Order etc. 

However, Zoho Inventory doesn't have custom function so many feature has to perform on Books instead of Inventory which caused a lot of trouble because some user uses inventory. 

Is it possible to add customer function on ZOHO Inventory too or I wrote my customer function on books and make it run on inventory? Zoho books cost only CAD$ 27 but Inventory cost me $77 and I really expected more value than it. 

Thanks a lot