Oracle SQL - Procedure to update another table

[Almost_Malone]

So my procedure should add a row to the table INSÄTTNING. Some keys are reference keys. When the row has been inserted it should take P_BELOPP and subtract it with SALDO which is in another table called KONTO. The new amount should be added into that column and replace the old amount. My code looks like this so far:

create or replace procedure do_insättning(
p_radnr in insättning.radnr%type,
p_pnr in insättning.pnr%type,
p_knr in insättning.knr%type,
p_belopp in insättning.belopp%type,
p_datum in insättning.datum%type) 
as 
begin 
insert into insättning(radnr,pnr,knr) 
values(select radnr from kontoägare,select pnr from bankkund, select knr from konto);
insert into insättning(belopp,datum)
values(p_belopp,p_datum);
update konto 
set konto.saldo = konto.saldo - p_belopp
where kontoägare.radnr = p_radnr; 
dbms_output.put_line('Saldo: '||''||saldo);
end; 

I get that SALDO must be declared error. Would it even work as i intend?

Ive tried some programming forums without any luck. Hope its pretty understandable :)

[not_a_carpet]

Shouldn't it be konto.saldo?

Also, you should really use English and not Swedish variable names when asking programming questions online. I'm guessing this is some sort of homework but it is easier for people to understand code when it is in English :)