Barry,
Sorry but you are hiding the actual code.
Here discount is referred to in SetupData() but not in createLines() as I see it.
We don't know what a_soimp and lo_line is. a_soimp might be an alias, or a memory variable pointing to an object (which in that case should be prefixed with m. to be safe - otherwise it is a source for error).

Error might be referring to a_soimp (if that is a variable) or lo_line 'xxx' property is not found. We don't see what they are and the actual code creating and using these.

>Thanks Thomas, I take your point.
>Below is the relevent code.
>Notice that "discount" is in the class constructor, and occurs in SetupData() and CreateLines() respectively.
>It does not complain in SetupData() which executes first but, but throws an exception in CreateLines() which executes immediately afterwards.
>But only in runtime does it throw an exception.
>
>

>DEFINE CLASS tdbflink AS tmessagelink
>
>	saveenvtries = 0
>	*/BarryT 07/17/2019 09:46:32 AM START 
>	discode = ""
>	discount = 0.00
>	*\BarryT 07/17/2019 09:46:35 AM END 
>	Name = "tdbflink"
>
>	PROCEDURE set
>		*-- we are on a new order, so create what we need, and save the info that we want
>		this.setupdata()
>		*-- Create all the necessary line items.
>		 this.createlines()
>
>	 ENDPROC
>
>
>	PROCEDURE setupdata
>		*-- Setupdata()
>		*-- get the standard stuff
>
> 		*/BarryT 07-17-2019 11:22:44 AM START
>		THIS.discode = Alltrim(a_soimp.discode)
>		THIS.discount = a_soimp.disc
>		*\BarryT 07-17-2019 11:22:45 AM END 
>
>	ENDPROC
>
>
>	PROCEDURE createlines
>		*-- Create lines for each of the order lines in this file.
>
>		        */BarryT 07-17-2019 12:37:17 PM START
>		        lo_line.discount = a_soimp.disc
>		        lo_line.discode = a_soimp.discode
>		        *\BarryT 07-17-2019 12:37:19 PM END 
>
>	ENDPROC
>
>ENDDEFINE
>

>