Error in Lexical Parameters in Oracle Reports 12c

I have created a report with lexical parameters. I am using Oracle Reports 12c. Here is my code:

SELECT &c act_date,&c1 act_amnt FROM &tble &s

In After Parameter Form trigger, I have written the code where I have substituted the lexical parameters value with actual table column names, tables and where clause from the Oracle Database (19c). I reproduce a sample of the code written in the After Parameter Form

function AfterPForm return boolean is

begin

:c := 'act_date';

 :c1 := '-1*SUM(NVL(act_amnt,0.00))/10000000';

 :tble := 'ACNTNG_TRNSCTN';

  

 IF :P_TYPE = 'LOC' THEN

  :s := 'WHERE act_acnt_code IN (''E01022'',''E01023'') AND act_date BETWEEN :P_FROM_DT AND :P_TO_DT AND ACT_NRTN NOT IN( ''A08009'') group by act_date';