如何计算microsoft excel中的日期时间差异？

I have two columns with datetime values in this format dd/mm/yyyy hh:mm:ss.How do i calculate the difference between two columns in minutes and show a value if it exceeds certain minutes. For example if the difference of column B - A is less than 5 minutes, than it should show 'ok' else it should show 'fail'. ExampleI have two columns with datetime values in this