I am assuming that you want some sort of validation based on yes/no check box and 'End of Day' and 'High Priority' are choices in a dropdown. If yes then you try below steps.
Create a yes/no column, a choice column with choices 'End of the Day', 'High Priority', a date column. Then navigate to list settings -> Validation settings and use below formula to ensure form performs validation at all times. In below formula 'YesNo' is a yesno column name, ChoiceCol is Choice column name and DateCol is date column name.
The above formula invalidates the form if the Yes/No column is true and either the dropdown and date column is blank. You can always use field description field to provide explanation on when to use a particular field (as we are not showing/hiding any fields here)