HI That a little bit complexes. 1-st way , you create script for calculation this day but you must remember so need calculate using SL for SLA or SC. 2-nd way you create rules where after creation SC copy Deadline and Max duration in other fields, then multiply Maxduration*.75 and set to Maxduration, you get value in Deadline field, this Value copy to New field ,example "75deadline" and copy back original Deadline and Max duration. Last rule(for variant 1 and 2) for notification must be shceduled on time "75deadline" where you must check status completed? if not send message.