I want to be able to see upcoming expiry dates on my excel spreadsheet

Hi there, I am currently making a equipment inventory list. One of my requirements is to put the inspection done date, and an inspection due date. I am also required to have a warning date that would give me a three month warning (turns red) when the inspection due date approaches. I have tried to make a formula but do not think I am approaching it right. So far i have =IF($I5<($H5()+90), "ALERT:DUE DATE","") does this make sense? If the warning date is less than the inspection date by 90 days highlight and alert:due date. please help me! I have attached a sheet so you can see exactly what I am doing.