Can you confirm that you have two data sources: transaction list and list of customers with first fill date?
If yes, data blending may work. Alternatively, table calculations might do the trick.
Attaching desensitized data sample would help.
Ok here's the table layout:
ID, Last Name, First Name, DOB, Address, Created Date, Last Access, etc etc
Patient ID, Rx Number, Refill Number, Date Filled, Drug ID, etc etc
I join these two (along with two or three other tables) to get
Patient, Rx Number, Date Filled, etc etc etc.
Selecting Patient for rows and min(rx.filldate) gives me a table of all the FIRST EVER fill dates for ALL patients.
You can try using calculated field with a formula like this:
//determine if ordered this week
DATETRUNC('week',NOW()) <= [Order Date] //start of current week
AND [Order Date] < DATEADD('day',7,DATETRUNC('week',NOW())) //end of current week
replace [Order Date] with your date of first fill and use this calculated field as your filter, keeping 'True'.