Task Due On Stage Not Date

Task Due On Stage Not Date

How can I add a task that has a due stage, not due date?

Eg; Our sales process in Zoho CRM goes through 12 stages and I need to create a task that is due when the 8th stage gets completed for a certain customer (ie; this is a one off task I need to create, not something for every customer every time stage 8 completes).

So how can I create tasks due by stage, and not due by date.

Any ideas would be greatly appreciated.