Below seems to be working but the script only evaluates the active row rather than every record in the portal
AddRemoveListItem ( If ( myTable::email = 1; myTable::description; "") ; "")
AddRemvoveListItem would appear to be a custom function so we aren't likely to know what it does.
If you are using FileMaker 12 or newer, you can set up ExecuteSQL to produce this list by using a WHERE clause to check for the value 1 in this field.
Using older versions or if you don't want to try to use SQL, you can set up a relationship that only matches to line items with the specified invoice ID that also only have a 1 in the field and then List() will list the correct values via that relationship.
Oh ya, forgot I added this a while ago.By: David HeadLet ([novalue = IsEmpty ( FilterValues ( theList ; value ) );listminusvalue = Substitute( "¶¶" & theList & "¶¶"; [¶ & value & ¶ ; ¶ ] ; ["¶¶¶"; ""] ; ["¶¶"; ""] ) ;listplusvalue = List ( theList; value )];If ( novalue ; listplusvalue ; listminusvalue ))I'm trying to create the relationship as you suggested but how would I assign a value of one in the field?I've tried below but it doesn't seem to be workingSet Field [myTableFilter::email;1]Go to Related Record [show only related; from table: "myTableFilter"; Using: <current>]Send Mail[Send via email client; subject: needed; List (myTable::description)Exit Script 
how would I assign a value of one in the field?
Define a calculation field with a number result type.
Enter this as your calculation:
Then include this field as an added match field in a relationship to your line items:
Invoice::__pkInvoiceID = LineItems|Selected::_fkInvoiceID AND
Invoice::constOne = LineItems|Selected::email
List ( LineItems|Selected::description )
would then produce a return separated list of Description values but only those where Email = 1.
LineItems|Selected is my name for a new Tutorial: What are Table Occurrences? of LineItems added so that you can keep your current relationship between the two tables unchanged.
Ok, got it. Thanks for the help!