Pop Up for clash info on sickness

Context: We had a manager who could not close a sickness report because of a clash with another Leave request. We realised it was one of the Bank Holidays (we use Compulsory Leave days for these), so the sickness report wouldn't close.

When the manager tried to close the sickness report, a message popped up about the clash, but it didn't indicate what the clash was. 

Request: It would be great if it worked similar to when booking a holiday it advises what the actual clash is. Thanks!