Filtering A Three Table Join With Optional Para

Hi.
I am working on a procedure which can filter data through three tables.
First Table is User
---------------------------
UserName UserID
---------------------------


Second Table is Customer
---------------------------
UserID Cust_Site_Int_ID
---------------------------

Third Table is l Details
---------------------------------------------------------------
Cust_Site_Int_ID Created_Date Status
----------------------------------------------------------------

I want to create a stored procedure which can filter through these tables. I will have four input fields in my application to accept parameters. The four parameters will be UserName, two date fields which specifies a range of dates and status. I want the filter to work like this, if only one parameter is provided it will use only that parameter if additional parameter is given it will use the AND logic.

I tried to do a Proc but it is not working any way here it is. So you will get a better idea of what I am trying to achieve.


set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go


-- =============================================
ALTER PROCEDURE [dbo].[FilterServiceTickets]
-- Add the parameters for the stored procedure here
@userName varchar(20)= NULL,
@startDate datetime =NULL ,
@endDate datetime = NULL,
@status int = NULL
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;

-- Insert statements for procedure here
SELECT SERVICE_TICKET.SERVICE_TICKET_CODE, SERVICE_TICKET.PROBLEM_REPORTED, SERVICE_TICKET.CONTACT_NUMBER,
SERVICE_TICKET.STATUS
FROM aspnet_Users INNER JOIN
BuildingAddress ON aspnet_Users.UserId = BuildingAddress.UserID INNER JOIN
SERVICE_TICKET ON BuildingAddress.Customer_Site_Int_ID = SERVICE_TICKET.CUST_SITE_INT_ID
WHERE ((aspnet_Users.UserName = @userName)OR (@userName=NULL))
AND ((SERVICE_TICKET.STATUS = @status) OR (status=NULL))
AND ((SERVICE_TICKET.CREATED_DATE >=@startDate AND SERVICE_TICKET.CREATED_DATE <=@endDate ) OR (@startDate=NULL)OR (@endDate=NULL)OR(@startDate=NULL AND @endDate=NULL))
END

Could some one please help me with this.
Thanks