Need a Formula for Conditional text to display in a Task planner

Dear All Valuable members need a urgent help ,

I am working on a task planner which approx has 3000 rows with different sub tasks , 5 to 6 tasks together makes a main task so i need to track the progress and make a dashboard for main task , in order to do that i have to manual feed in sub task status (which keeps changing eg. work which was not started now completed or overdue ) so i need to put a formula to put in main task column which will look all 5-6 task in Sub task column and tell me the final status as per the condition applied , attaching the sample file please help , and thanks in advance