Program with Multiple Entries and Updating Data Points

Hi,

I am trying to create a Program that will allow me to send an e-mail to an individual who is in different courses (so they may get the program multiple times) BUT only send it to them one time when they hit over 25% but less than 50% of their work done.  My issue is that the number pulled for 25% is constantly updating.  So if they hit 25% today and 30% tomorrow they could potentially receive this campaign multiple times for the same entry.

My sql view looks like this:  select  a.RIID_, b.INSTANCE_ID, b.CUSTOMER_ID, b.EMAIL_ADDRESS_ , b.COURSE_NAME, b.PERCENT_COMPLETE, b.GRADE from $A$ a JOIN $B$ b ON a.CUSTOMER_ID = b.CUSTOMER_ID where (PERCENT_COMPLETE between  '.25' AND '.49')  and GRADE > 70