i am doing work schedule assignment for my group of 18 people on excel.
i sometime assign one person to two different posts by mistake. what is the
best way to check for redundancy?

the excel file looks as following"

( day) 1 2 3 4 ....... 31
Jan position 1 Mr. A Mr. B Mr. C Mr. D
position 2 Mr. B Mr. C Mr. D Mr. E
position 3 Mr. C ......