Overlap among multiple activities

Goodmorning,
I'm Andrea and I've got a problem (I feel like in a mutual aid fellowship, haha).
I've to apologize about my English because I'm Italian.
Part of my job is supposed to make salaries of other people in our cooperative company.
Everyone have this template, time table.xlsx. Everyday, everyone have 4 boxes (2 ins, 2 outs) per 25 activities. Somebody work among multiple activities, somebody work in just two, or maybe only one.
The meaning of two ins and two outs is to let people have lunch, or a break, and return to their job in the same day.
We count every 15 min.

I'd going crazy looking for a way to count and show days in when there's an overlap. This, in order to solve any errors that may appear.
I'm pretty sure I'm not clear in what i mean. If so, please ask me, and I'll define better my idea.
Thanks a lot,

Have everybody a great weekend.


Andrea

Hi Amanda
If you use Data Validation rules you will not need to do a COUNTIF for overlapping times. Have a look at the Data Validation rules I have added to cells D4, F4 and G4 to see what I mean.
Hope this helps.
Tony