Is there a way to program a count-down timer in Excel?

For example, say I need to buy toner cartridges every 3 months, and I just
bought some. Then I can reset the timer, and it'll indicate another 3
months. When the three months are up, another cell will turn go from "Toner
in stock" to "Buy toner."

Does anyone know how to program excel to do something like this? Thanks!