Filtering A Custom Paged Stored Procedure

Hi,
    I am trying to implement filtering on a custome paged stored Procedure, here is my curent Stored Procedure which doesn't error on complie or run but returns no records. Anyone got any ideas on how to make this work???
<Stored Procedure>
set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go

-- =============================================
-- Author:        Peter Annandale
-- Create date: 22/10/2006
-- Description:    Get Filtered Names
-- =============================================
ALTER PROCEDURE [dbo].[proc_NAMEFilterPaged]
    -- Add the parameters for the stored procedure here
    @startRowIndex int,
    @maximumRows int,
    @columnName varchar(20),
    @filterValue varchar(20)
AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

SELECT CODE, LAST_NAME, Name, TYPE, NUMBER
    FROM
        (SELECT n.CODE, n.LAST_NAME, n.FIRST_NAME + '  ' + n.MIDDLE_NAME AS Name, nt.TYPE, f.NUMBER,
            ROW_NUMBER() OVER(ORDER BY n.LAST_NAME) as RowNum
        FROM dbo.NAME n
            LEFT OUTER JOIN NAMETYPE nt ON n.NAME_TYPE = nt.NAME_TYPE
            LEFT OUTER JOIN FUNERAL f ON n.CODE = f.DECEASED
        WHERE @columnName LIKE @filterValue
        ) as NameInfo
    WHERE RowNum BETWEEN @startRowIndex AND (@startRowIndex + @maximumRows) -1
END
 
</Stored Procedure>
 
Any assistance would be greatly appreciated..
 
Regards..
Peter.