How to update story based on ruless on subtask description and dates

[Vijay Nayak]

Hello - 

I have Jira stories, and various subtask to it. Story and Subtask follows a naming convention as shown below. 

Story Name - createMyCoffee

Subtasks - 4 of them(Prefixed by Story name)

createMyCoffee_BuyingMik

createMyCoffee_BuyingSugar

createMyCoffee_BuyingCoffee

createMyCoffee_MakingCoffee

I want to update Story workflow field with BuyingMilk, BuyingCoffee, BuingSugar or MakingCoffee based on key word in Subtask description and, the start and end on the subtask.

So condition would be if subtaks description has BuyingMilk, and start date is greater than TODAYs' date and end date is not updated(meaning subtask is Open) - set the story workflow field to BuyingSugar status. Is that doable?