Formatted Search Query for DocCur in ORDR

Hello,

i need help with a query for a formatted Search.

During adding a new Order:

If CardCode = '20015' THEN 'USD'

my Query only works as FMS, but not during adding a new Order:

Select CASE
When $[$4.0.0] = '20015' THEN 'USD'
ELSE $[$63.0.0] END


....

SELECT 'DocCur'=
CASE 
WHEN $[ORDR.CardCode] = '20015' THEN 'USD'
ELSE $[ORDR.DocCur] END

1). [Microsoft][SQL Server Native Client 11.0][SQL Server]Incorrect syntax near 'ORDR.DocCur'.

Where is my mistake ?

Thanx

Markus