how to make line of business mandatory in incoming payment(orct) receipt if row is selected

[ASHFAQUE]

Dear Sir 

How to make Line Of business(OcrCode3) mandatory in incoming payment receipt if row is selected in receipt (rct2)

i write code but its not working: 

Cnt1:=0;

if :object_type='24' and (:transaction_type='A' or :transaction_type='U') then

SELECT Count(*) into Cnt1

FROM RCT2 T1

WHERE IFnull(T1."OcrCode3",'')= '' AND T1."IsSelected"='Y' AND T1."DocEntry" = :list_of_cols_val_tab_del;

if :Cnt1>0 then 

error := 1;           

error_message := 'You are not allowed to POST WITHOUT line of business';

end if;

end if;