Exception in PLSQL

Question

Hello,
I have a problem to catch exception in this proc :
create or replace procedure MAPROC (nom_snapshot in varchar2) is
ladate varchar2(20);
BEGIN
select sysdate into ladate from dual;
dbms_snapshot.refresh(nom_snapshot);
execute immediate 'UPDATE update_snapshot set DATE_REFRESH = to_date(''' || ladate || ''') where nom_snapshot = '''|| nom_snapshot || '''';
COMMIT;
EXCEPTION
WHEN OTHERS THEN
execute immediate 'UPDATE update_snapshot set ERREUR = ' || SQLERRM || ' where nom_snapshot = '''|| nom_snapshot || '''';
END;
the proc MAPROC is in called in :
DECLARE
nom_snapshot varchar2(50);
cursor c1 is select b.nom_snapshot from user_snapshots a
begin
open c1;
loop
fetch c1 into nom_snapshot;
exit when c1%NOTFOUND;
MAPROC(nom_snapshot) ;
end loop;
close c1;
end;
the second proc is in error because i can't catch the error in the exception step of MAPROC. However, the error is due to the following step in MAPROC :
dbms_snapshot.refresh(nom_snapshot);
How can i do to catch the exception in MAPROC, and not allow it to climb in the second proc.
Thanks

Answer 1

Thanks for all your answers.
I'm too busy today to test every remarks you've made.
however, i just want to explain the final goal of the procs. maybe it will be easier for you to find a solution, or a better way to do this :
i want to make a proc that refresh oracle snapshot.
so i put in a cursor the list of snapshot for the oracle user
(select name from user_snapshots)
then for each snapshot name, i have to do :
truncate trable "snapshot name"
dbms_snapshot.refresh("snapshot name")
update TABLE set date = "sysdate" where snapshot_name = "snapshot name"
if it fails, principally, the refresh step which it a source of pbs, i want to do :
update TABLE set error= "Oracle error" where snapshot_name = "snapshot name"
So to do this, i thougt it will be better to divide the work in 2 step (and procs) :
the first proc which select the list
the second proc, which is doing the refresh, etc ... for every snapshot.
so if you think my method is not the good one, I'm open to try another.
but, don't use something to hard, i'm not an PL/SQL expert, but you surely already know this.
J.