Pulling data from two tables into one report...

I have a field that isn't getting put into a table and need to refer to that particular column to do some calculations.

Tables: 112 - Sales Invoice Table, 21 - Cust. Ledger Entry

The field I am trying to gather is External Document No. which is in table 21 and I want to reference it based on 112.

I have included both tables, but am unable to pull the column from one that I need:

I tried this in OnAfterGetRedord:

IF "Sales Invoice Header"."No." <> '' THEN
item.GET("Sales Invoice Header"."No.")
ELSE
CLEAR(item);
ExtDocNum := (item."External Document No.");

I get the following error: "The expression Code cannot be type-converted to a Option value"

Any leads or ideas will be appreciated greatly.

[SOLVED]