Update Trigger... Best Solution

Hi All

I have two questions:

1. the below trigger, is it the best way to update a inserted or updated column?

Create trigger tr_update_acc_status
on customer
for insert, update
as

begin
update customer
set deleted = 1
where account_status = 4 and account_status = 6
end

begin
update customer
set deleted = 0
where account_status = 5
end

it works ok but takes a long time to update the deleted column as it scans all records, which takes me on to my next question:

2. is it possible to amend the quiry above to it only updates the record i have added or updated



Thanks