Is it possible to create monthly pop up/ email alert per client type?

For example I have 3 clients' category : GOLD / SILVER / BRONZE

GOLD clients need to be called once a month

SILVER clients need to be called once every 3 month

BRONZE clients need to be called once every 6 month

I would like to have a alert when the Sales have reach the time to call them (i.e. last call for a GOLD client was more than 1 once ago).

Thanks a lot for your help !