Here is an example of a hidden filter that selects all the employees in an HR system and adds them to the instance list:
Notice that the filter is not visible. This filter has a uInitialize routine like this:
Mthroutine Name(uInitialize) Options(*Redefine)
* Do the ancestor thing ....
Invoke #Com_Ancestor.uInitialize
* Define this as a hidden filter ( you can only ever sensibly have a
* single filter when it's hidden )
Set #Com_Owner avHiddenFilter(TRUE)
* Now fill the instance list with all employee details
Invoke #avListManager.BeginListUpdate
Invoke #avListManager.ClearList
Select Fields(#EmpNo #SurName #GiveName) From_File(PSLMST)
Use BConcat (#GiveName #SurName) #Std_TextL
Invoke Method(#avListManager.AddtoList) Visualid1(#Empno) Visualid2(#Std_TextL) Akey1(#Empno)
EndSelect
Invoke #avListManager.EndListUpdate
* Finished
EndRoutine