Help with times

Hello Guys, currently I am working on an excel sheet that my boss has asked me to do. The excel table has cells in time format; for example, 00:00:00 for 12 am, and 00:05:00 for 12:05 am. My boss would like the table to highlight the cell that contains 00:00:00 if the current time is between 12:00:00 a.m. and 12:04:59 a.m. And highlight 00:05:00 if the cell is between 12:05:00 a.m. and 12:09:59 a.m.

I understand that somehow this is doable with custom formatting (correct me if I'm mistaken please) However, I have not found the way to make this work. Can you please help me on this? I only know about excel when it comes to finance.

Thanks in advance.