Error coming for CE_CALC Plan operator

Hi to all,

I am using CE_CALC Operator, code is below, but i am getting error.

/********* Begin Procedure Script ************/

BEGIN

TV = CE_COLUMN_TABLE("YTABLE");

TV1 = CE_PROJECTION(:TV, [ "PART", "SITE1"  ,

        CE_CALC( ' IF ( "PART" = "A","X","Y" ) '  ,   NVARCHAR(2)) AS  "TXT" ] );

END;

/********* End Procedure Script ************/

Error: Error creating procedure;Attribute not found in column table: A: line 9 col 9 (at pos 337) at ptime/query/checker/proc_check_cefunc.cc:707

But "PART" Field have entry "A" in table "YTABLE".

please let met me know where is error ?.

Regards

Pavneet Rana