How to detect name of tt table?

Im trying to pass a cost.groupid to my 4gl code in Data Drirectives

Costing Workbench / Action / Post
there is a form [Cost Post Set].

my action code is:
create UD01.
assign UD01.Company = ttCostGrp.Company
UD01.Character01 = ttCostGrp.Description.
I cannot find any records in UD01 table (via SQL)

when I change my action code to:
create UD01.
assign UD01.Company = "Company"
UD01.Character01 = "Description".

I can see records in UD01 table.

I quite sure that there is no ttCostGroup in [Cost Post Set] window.
What is the name of table I can use in 4gl code?

Best Regards