Sum minutes between child records

I can't thank you all enough for your direction.  But how would you edit this so that it doesn't create a new record for the 'stop', but just edits it?  I think the 'start' should create a new record.  I can't seem to figure out what the latest record to use API_EditRecord on for the edit of the new stop field.  Here is my code that has an if statement that dynamically changes the URL:

// Create Start Child Record
var text URLSTARTONE= 
URLRoot() & "db/" & [_DBID_TICKET_TIME_HISTORY] 
& "?act=API_AddRecord&_fid_8=" & URLEncode ([Record ID#])
& "&_fid_6="&URLEncode("Start")
& "&_fid_7="&URLEncode(Now());

//Change Start Parent
var text URLSTARTTWO = 
URLRoot() & "db/" & Dbid () & "?act=API_EditRecord&rid=" & [Record ID#]
& "&_fid_12="&URLEncode("O-In-Progress")
& "&_fid_17="&URLEncode("O-In-Progress")
& "&_fid_14="&URLEncode(Now());
//& "&rdr=" & URLEncode(URLRoot() & "db/xxxxxxxxxxx?a=td");

// Create Stop Child Record
var text URLSTOPONE= 
URLRoot() & "db/" & [_DBID_TICKET_TIME_HISTORY] 
& "?act=API_AddRecord&_fid_8=" & URLEncode ([Record ID#])
& "&_fid_6="&URLEncode("Stop")
& "&_fid_7="&URLEncode(Now());

//Change Stop Parent
var text URLSTOPTWO = 
URLRoot() & "db/" & Dbid () & "?act=API_EditRecord&rid=" & [Record ID#]
& "&_fid_12="&URLEncode("O-Stalled")
& "&_fid_17="&URLEncode("O-Stalled")
& "&_fid_14="&URLEncode(Now());
//& "&rdr=" & URLEncode(URLRoot() & "db/xxxxxxxxxxx?a=td");

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

If(
[Status]="O-Stalled",
$URLSTARTONE 
&"&rdr="&URLEncode($URLSTARTTWO)
&URLEncode("&rdr="&URLEncode($URLTHREE))
,
$URLSTOPONE 
&"&rdr="&URLEncode($URLSTOPTWO)
&URLEncode("&rdr="&URLEncode($URLTHREE))
)