if not exists problem

[plork123]

hi all

i'm trying to do an 'if not exists statement... ' but it errors in the query window

this is my code


if not exists (select 1 from mytable where field1 = ??? and field2 = ???) then
insert into mytable values ('???','???','???');
else
update mytable set field3 = '???' where field1 = ??? and field2 = ???;
end if;


i'm using mysql version 4.0.25, does anyne know how i can do this statement in mysql 4.0.25?

thanks for any help