OBIEE - Filter SQL Expression Not Working At All - Shows SQL But Not Result

Question

Im at my wits end for this
I have a report where I am using a filter with a simple SQL expression
cast ( timestampadd(SQL_TSI_YEAR, -1, Cast(Cast(DATE '@{pv_as_of_date}{2013-04-01}' AS CHAR) AS TIMESTAMP) ) as DATE)So an end user may input a date and this is passed into the filter via a variable
pv_as_of_date
This is defaulted to 2013-04-01
I want to subtract 1 year to make the end result
2012-04-01
When I run the report I am seeing two issues
1) When displaying the filter at the bottom, I see the full SQL code. Shouldnt this show the date returned? In this case shouldnt the filter show 2012-04-01?
2) The filter does not even work which is my bigger problem
I tested the above code in a column and I KNOW that the date is being returned as expected
But when I use the same SQL code in the filter then it doesnt work
Am I missing some special button some where to enable SQL expressions?
Any help immensely appreciated

Answer 1

Ok
So I was able to find an option "Protect Filter" that seemed to make a bit of difference and I got the date part working after using the above corrected code (thanks)
But now I want to add in the rest of my filter conditions and it does not seem to be liking it
Im trying to use this filter
'Acad ' || cast ( cast (substring ('@{pv_acad_year_desc}{Acad 2013/14}' , 6, 4) as integer) - 1 as char(4)) || '/' || cast ( cast (substring ('@{pv_acad_year_desc}{Acad 2013/14}' , 11, 2) as integer) - 1 as char(2))Im expecting the output to be in this case
Acad 2012/2013
When I test the above code in a column it works just fine, its just again in the filter that it isnt working