Lookup value using table variable. Cannot find table variable

[Anonymous]

Hi

I am trying to simplify my dashboard modeling by using a table variable instead of creating an actual table and lookupvalue from there. The problem is when I try to lookupvalue from table it says it is expecting a basetable instead. here is the code

Classify by Customer SalesDocType =

  VAR
_table_var = GROUPBY(ama_west_customer_mapping_tbl, ama_west_customer_mapping_tbl[SoldToParty], ama_west_customer_mapping_tbl[SalesDocType], ama_west_customer_mapping_tbl[Order Acquisition Classification])

RETURN

    LOOKUPVALUE(_table_var[Order Acquisition Classification], _table_var[SoldToParty], sales_document_header_data_tbl[SoldToParty], _table_var[SalesDocType], sales_document_header_data_tbl[SalesDocType])