Trigger an email off an activity creation

I'm trying to trigger an email to send 3 days after an activity is opened if the task is still open.  The workflow isn't working and I think it is because the activity is created off another activity being completed.  Here is an example:

SR is opened which triggers task 1

Task 1 is modified to completed status which triggers task 2

Task 2 is modified to completed which triggers task 3

I want to schedule a wait of 3 days from when task 2 is created.  After the wait period, the condition would be if the task type= task 2 and status <> completed, then trigger an email.  I can only get this to work if I select when an activity is modified.  Any suggestions on how I can get this to work?