Thank you @Luis Angel Pérez Ramos I used your suggestion and it worked.  Thank you @Jeffrey Drumm for showing me how to set the EXTRACT function. I used $EXTRACT(context.ObxTrunc,1,470) where context.OBxTrunc is the context variable holding the original message.  

In the BPL, I passed the message through the newly created DTL that was looking if the OBX 5 characters(bytes) were greater than 400, if so, I took the substring of the first 470. (I tried taking 480/ 490/ 500 but that would cause the message to error) then following Luis's suggestion, I defined another context variable with the same type than the original message as output. 

@Jeffrey Drumm please see below. 

Error 1:

ERROR <Ens>ErrException: <SUBSCRIPT>zExists+1^Ens.Util.FunctionSet.1 ^Ens.LookupTable("TestTable","The patient came in accompanied by their daughter.. Time-out was -- logged as '-' number - @''
 

Error 2:

ERROR <Ens>ErrBPTerminated: Terminating BP TestRsltRouter # due to error: ERROR <Ens>ErrException: <SUBSCRIPT>zExists+1^Ens.Util.FunctionSet.1 ^Ens.LookupTable("TestTable","The patient came in accompanied by their daughter.. Time-out was -- logged as '-' number - @''
> ERROR <Ens>ErrException: <SUBSCRIPT>zExists+1^Ens.Util.FunctionSet.1 ^Ens.LookupTable("TestTable","The patient came in accompanied by their daughter.. Time-out was -- logged as '-' number - @''
 

I like the idea BUT I still want the original OBX 5 values to be received as is downstream without being truncated and my fear is that by truncating the OBX 5 values greater than 510 characters before passing on to subsequent DTLs I will pass on incomplete fields. Hope that makes sense 

Thanks for your response @LuisAngel.PérezRamos. I should have included in my post that this interface is designed not to have any rules. Only 1 BPL and DTLs. Any way I can use $EXTRACT within the BPL?

Thank you @Julian.Matthews7786 for the clear and concise response, it worked! Thank you @Arshiya Syeda and @Ashok Kumar T as well for giving me something to start working with.
 

Thank you @Julian.Matthews7786. I will try your suggestion. 

@Ashok Kumar T Thanks for the reply. My greatest challenge is how to pull that PV1 7 value given that there are different providers e.g, 'TEST,PROVIDER', 'TEST,PROVIDER1', 'TEST,PROVIDER2', 'TEST,PROVIDER3' etc. I might be missing something in the code that you sent or might not be clearly understaning it. Thanks 

@Arshiya Syeda 
Thanks for the reply. My greatest challenge is how to pull that PV1 7 value given that there are different providers e.g, 'TEST,PROVIDER', 'TEST,PROVIDER1', 'TEST,PROVIDER2', 'TEST,PROVIDER3' etc. so I can not hard code it to only use 'TEST,PROVIDER'

Thank you @Luis Angel Pérez Ramos 

Hi @Luis Angel Pérez Ramos 
Thank you, the code worked perfectly in the BPL. How can I change it to work in the DTL?

I need to search for the following values "SEDATION:  " and "Procedure" In consecutive OBX 5 and if true set OBR 4.1 = "28014-9"

OBX|028|TX|OP^Operative Note^D4D^11504-8^Surgical operation note^XXX||SEDATION:  ||||||C|
OBX|029|TX|OP^Operative Note^D4D^11504-8^Surgical operation note^XXX||Procedure:

Thank you @Luis Angel Pérez Ramos 

Hi Luis, thanks for your response. However, the interface in question doesn't have a rule, only BPL. All the routing gets determined by the BPL. 

Hi @Alex Woodhead 

At which point do we actually specify the lookup table we are searching against in the function? In my case, the table is AnemiaResults 

Thanks. Will have a look

The challenge is that the text does not follow any particular order :-(

Thanks for your reply. Will try it out 

Edited to add:

Would Set value = $Piece(obxValue, "<>", *) work?