Conditional formatting of a cell

[corsair_lancer]

Hi. I wish to create a condition on which cells turn red if there is a difference in value between two other cells. Specifically, it is a time difference.


ie:
A shift begins at aa:bb (hours:minutes).
Patient x arrives at aa:bb.
If the difference between the beginning of the shift and the arrival time is longer than 12 hours, cell x will turn red (so as to notifiy us that said patient has been for longer than 12 hours without being hospitalized).
Best regards.
Claudio