Help With Date Parameter And If/else Statement

Hi,

I'm trying to run a select statement that takes includes an if/else
clause. I need to select the 'tran_date' between....

if the current month is greater than 10 i.e. after OCT then the
tran_date will be between '01-Oct' - plus current year or the
tran_date is '01-Oct' plus previous year.

and the current date

Here is my script so far:

SELECT a.resource_code ASSOCIATE, a.tran_date START_DATE,
b.description PROJECT_CODE, sysdate
FROM actrans a, acactivity b, dual c
WHERE a.resource_type = 'E'
AND a.acct_category = 'TIME'
and a.activity like '9-WW-357852%'
and b.activity = a.activity
and tran_date between

if to_char(sysdate, 'MM') > 10)
begin
a.tran_date = '01-Oct' & to_char(sysdate, 'YY')
end
else
begin
a.tran_date = '01-Oct' & to_char(sysdate, 'YY'- 1))
End
ORDER BY tran_date

Can anyone help me out with this? I need to run it as a job, but not
sure whether I should be using a stored procedure etc..

Thanks in advance.
George