Hi Jelmer,
If I understand you correctly then 01-09-2019 is the day you swapped to a new system, so, all new cases starting after that day will use the new names? The way to merge the formulas is to use a case when statement.
Heres my suggestion for the formula

AVG( CASE WHEN DAYS_BETWEEN(PU_FIRST(YOUR CASE TABLE,XXCEL_AP_ACTIVITIES.EVENTTIME), TO_TIMESTAMP(01-09-2019, DD-MM-YYYY)) > 0

THEN CALC_THROUGHPUT(FIRST_OCCURRENCE[ Ontvang Factuur ] TO LAST_OCCURRENCE[Valideren Factuur], REMAP_TIMESTAMPS(XXCEL_AP_ACTIVITIES.EVENTTIME, HOURS))
ELSE
CALC_THROUGHPUT(FIRST_OCCURRENCE[ XXAIMG: Ontvangen in APRO Imaging ] TO LAST_OCCURRENCE[Valideren Factuur], REMAP_TIMESTAMPS(XXCEL_AP_ACTIVITIES.EVENTTIME, HOURS))
END)
DAYS_BETWEEN() returns a negative number if the second date argument takes place before the first. So by testing DAYS_BETWEEN(PU_FIRST(CASE TABLE,XXCEL_AP_ACTIVITIES.EVENTTIME), TO_TIMESTAMP(01-09-2019, DD-MM-YYYY)) > 0, all the cases for which there first activity takes place before the cut off are using the old activity name and all cases that start after it use the new name.
Does this solve your problem? Is there anything else we can help you with?
Best wishes,
Calandra

---

Dear Calandra,
This works perfectly! Thank you very much!
Kind regards,
Jelmer

---