It doesnt seem like you have server and unless you have your copy of Pro open all the time, then there isnt any native way to send you the email. If you decide to get server or have a copy of FM open at least once a day, you can have a script that fires upon opening or use Install OnTimer to check if the emails have been sent and if not send.
You would find for a set of records that are 3 days prior to the end date.
Enter Find Mode 
Set Field [ EndDate; Get ( CurrentDate ) + 3]
Set Error Capture [ On ]
Set Error Capture [ Off ]
If [ Get ( FoundCount ) ]
I didnt get into the details on how you wanted to send the emails. Either you can send it to the set or you can loop through the records.