<I have created a store ledger.
Aside the other columns, there are three main columns, namely, "Receipt" column, "Issue" column and finally the "Balance" column. Items received will be recorded in the "Receipt" column. Items issued out will be recorded in the "Issued" column. The "Balance" column keeps the running balance after "Issue" is deducted from "Receipt". I wish to set a threshold such that once the running balance reaches ZERO, users can't enter value on the "ISSUE" column. Put differently, I don't need negative balance as currently obtained. How can I achieve this? />