I have 2 scenarios that I need to cater for.
Cannot proceed (Cannot submit the form) - this is a calculation that stops the user from submitting th form; behaves like a required field maybe. An example the number of people found to have a positive HIV test cannot be greater than the total of number of patients tested.
Warning (Shows a message so that the user is aware but can still submit) - this is a situation where the counts are made into a proportion and compared with a percent. If the proportion is greater than or less than a threshold, it’s suspiciously incorrect, but the data entry person can still proceed and submit.