Business Rule that can compare two fields in a repeating segment

I am trying to find the best way to evaluate if OBX-3 = ^IS TEST PATIENT? and OBX-5 =  Y In the same OBX in a Business Rule

OBX|1|NM|P-CSN|1|7623201922192||||||F
OBX|2|NM|P-UCI|2|||||||F
OBX|3|TX|^ADT: PATIENT CLASS|1|Outpatient|||||||||20210715
OBX|4|TX|^IS TEST PATIENT?|1|Y

I started to create a function in a class that uses the Rule [] bracket syntax and  extends  Ens.Rule.FunctionSet:

But after some initial troubleshooting I realized that the [] brackets will not return a value if a field is null, making the two lists different lengths and impossible to compare.

HL7.[OBX:3] = <P-CSN><P-UCI><^ADT: PATIENT CLASS><^IS TEST PATIENT?>

HL7.[OBX:5] = <7623201922192><Outpatient><Y>

HL7.[OBX:5]  list has 3 values instead of 4 because the 2nd OBX-5 is null.

Has anyone come up with a way to do this easily in a rule or do I have to try to pass the entire HL7 message into a function to compare a repeating segment like this?

Here is the function I started

PairedValuesInLists(HL7.[OBX:3],HL7.[OBX:5],"IS TEST PATIENT?","Y")

ClassMethod PairedValuesInLists(list1 As %String = "", list2 As %String = "", value1 As %String, value2 As %String) As %Boolean [ Final ]{$$$LOGINFO(list1_"^"_list2_"^"_value1_"^"_value2)set list1 = ##class(Ens.Util.FunctionSet).ReplaceStr(list1, "><", ",")set list2 = ##class(Ens.Util.FunctionSet).ReplaceStr(list2, "><", ",")set list1 = ##class(Ens.Util.FunctionSet).Strip(list1, "*", "<>")set list2 = ##class(Ens.Util.FunctionSet).Strip(list2, "*", "<>")et returnValue = 0for i=1:1:$length(list1,",") 
  {
  set list1Value = $piece(list1,",",i)
  set list2Value = $piece(list2,",",i)
 
  w list1Value, !
  w list2Value, !
  if ((value1 = list1Value) && (value2 = list2Value))
  {
  set returnValue = 1
  }
 
  }
  quit returnValue}