Needs Another Field for UOM Convertion

I am using FA in a retail store. The stocks purchased comes in different UOM that what is sold. Each UOM have different code. I want to run a procedure daily that checks if the smaller UOM is negative and if so convert the bigger UOM to it. To do this I need a field for quantity/case. Is it alright if I create a new table in the database for this or can i use the long description in stock master? Thank you for the help.