Accounting Tax Codes: how to access records through SuiteScript?

Hello,
I've found a problem in NetSuite. Here's my scenario:

- I've created a "Other Custom Field" (CUSTORECORD_XXX) for record type "Tax Code"
- I've created a "Transaction Column Field" (CUSTCOL_YYYY) for Vendor Bill, with the same data type of the previous field, sourcing from "Tax Item"."CUSTORECORD_XXX"

The sourcing in the column field doesn't work: when selecting a Tax Item in a Vendor Bill item line, the "CUSTCOL_YYY" column is not loaded with the value of the selected tax item's CUSTORECORD_XXX field.


So I tried to do a workaround through a client script, but when I have to load the selected tax item record, I don't know wich record type I must specify to the nlapiLoadRecord function (I've tried with "taxitem", with no chance).