HELP ME, Плиз!!!

CREATE PROCEDURE TEST 
AS
DECLARE VARIABLE b smallint;
DECLARE VARIABLE NMax integer;
DECLARE VARIABLE CN  VARCHAR(255);
DECLARE VARIABLE TCN  VARCHAR(255);
BEGIN
  b=0;
  NMax=GEN_ID(NEW_MSG,0)-1;
  if (NMax>=0) then
     begin
        /*Следующая выборка работает*/
        CN='O666KT__';
        Select F_GN from T_USB_LIST where (F_GN like :CN) into :TCN;
        if (TCN<>'') then
           begin
           Update t_data_msg set F_GN=:TCN where (F_NUM=:NMax);
           end
        end
     end
END

CREATE PROCEDURE TEST 
AS
DECLARE VARIABLE b smallint;
DECLARE VARIABLE NMax integer;
DECLARE VARIABLE CN  VARCHAR(255);
DECLARE VARIABLE TCN  VARCHAR(255);
BEGIN
  b=0;
  NMax=GEN_ID(NEW_MSG,0)-1;
  if (NMax>=0) then
     begin
     Select F_GN from t_data_msg where (F_NUM=:NMax) into :CN;
     if (SubStr(CN,7,1)='?') then
        begin
        b=1;
        CN=strstuff(CN,7,1,'_');
        end
     if (SubStr(CN,8,1)='?') then
        begin
        b=1;
        CN=strstuff(CN,8,1,'_');
        end
     if (b=1) then
        begin
        TCN='';
/*!!! А тут уже нет, хотя CN, вроде, такой же...*/
        Select F_GN from T_USB_LIST where (F_GN like :CN) into :TCN;
        if (TCN<>'') then
           begin
           Update t_data_msg set F_GN=:TCN where (F_NUM=:NMax);
           end
        end
     end
END

Select F_GN from T_USB_LIST where (F_GN like 'O666KT__') into :TCN;

CN='O666KT__';
Select F_GN from T_USB_LIST where (F_GN like :CN) into :TCN;

Select F_GN from T_USB_LIST where (F_GN like :CN) into :TCN;