Reference previous record on formula (please assist)

Reference previous record on formula (please assist)


I am attempting to do a calculation inside of a Zoho Creator application.  I need do math on the following formula:

(Todays_Inventory) - (Todays_Shipment) - (Yesterdays_Inventory).

However I do not want the person to have to manually type in yesterday's inventory, because it is already in the system under a different record (in the Todays_Inventory section on the previous record).  How can i tell the formula to look back 1 record to obtain this information?