Creating two records at once with reference fields NOT being populated

Hi there. 

I am trying to use formula URLs to create a button that can make two child orders based on the parent order (where the button would be pushed) using API_AddRecord.

The child orders are supposed to duplicate some information from the parent order. The problem here is that reference fields are not being duplicated (unless you use the API_GenAddRecordForm which doesn't allow for creating multiple records
simultaneously).

Here's the code I've been using:

var text addOrderNumber = Left([Order #],".") & "." & ToText([Number of Change Orders] + 1) & ".ADD";
var text returnOrderNumber = Left([Order #],".") & "." & ToText([Number of Change Orders] + 1) & ".RETURN";
var text parentOrderNumber = Left([Order #],".");


//The URL to create a copy of the order. By default this is of type return order
var text CreateAddRecord =URLRoot() & "db/" & Dbid() & "?a=API_AddRecord"&"&apptoken=XXXX"
& "&_fid_6=" & URLEncode($addOrderNumber)
& "&_fid_59=" & URLEncode([Customer Number#])
& "&_fid_36=" & URLEncode([Partner Name]) // reference field
& "&_fid_35=" & URLEncode([Related Partner]) // reference field
& "&_fid_177=" & URLEncode([Partner Name]) // text field copying value of reference field


var text CreateReturnRecord = URLRoot() & "db/" & Dbid() & "?a=API_AddRecord"&"&apptoken=XXX"
& "&_fid_6=" & URLEncode($returnOrderNumber)
& "&_fid_59=" & URLEncode([Customer Number#])
& "&_fid_36=" & URLEncode([Partner Name]) // reference field
& "&_fid_35=" & URLEncode([Related Partner]) // reference field
& "&_fid_177=" & URLEncode([Partner Name]) // text field copying value of reference field

var text ROOTURL = URLRoot() & "db/" & Dbid() & "?a=dr&rid=" & [Record ID#];


$updateNumberofChangeOrder
& "&rdr=" & URLEncode($CreateAddRecord)
& URLEncode("&rdr=" & URLEncode($CreateReturnRecord))
& URLEncode(URLEncode("&rdr=" & URLEncode($ROOTURL)));

When we hard code one of the reference fields (& "&_fid_35=5" ) it still doesn't populate the field in the child order.

Please advise how I dynamically create two records with reference fields populated.