Hmmm... Well here is a quick sample SP I just wrote that should help you with the variable usage.

USE pubs

GO

-- First check to see if the sproc exists and if so drop it.

IF EXISTS(SELECT * FROM sysobjects WHERE id = object_id('MySampleSproc'))

    DROP PROCEDURE MySampleSproc

GO

/*---------------------------------------------------------------------------------------

Name: MySampleSproc

Description: sample procedure for how to use variables.

Sample Call:

DECLARE @nAuthorID varchar(11) , @dtStartDate datetime

SET @dtStartDate = convert(datetime,'01/01/1989')

EXEC MySampleSproc 'Green', @nAuthorID OUTPUT, @dtStartDate

SELECT @nAuthorID AuthorID

History:

    3/24/2004      gary johnson    Created

---------------------------------------------------------------------------------------*/

-- Now create the sproc

CREATE PROCEDURE MySampleSproc

    (

    -- Add in the parameter variables

    @nMyVar              varchar(40) -- Input only

    , @nMyVar2           varchar(11) = NULL OUTPUT -- Assigns default value and allow output of variable

                                            -- Also makes variable not be required to call

    , @dtMyVar3          datetime = NULL

    )

AS

BEGIN -- Procedure

    DECLARE -- Procedure Level Variables

        @dtMyVar4          datetime

    SET @dtMyVar4 = GetDate()

    IF @dtMyVar3 IS NULL

        BEGIN

            SET @dtMyVar3 = GetDate() - 50

        END

    -- Get AuthorID

    SELECT @nMyVar2 = au_id

    FROM dbo.authors

    WHERE au_lname = @nMyVar

    -- Now show All Sales for this author between today and @dtMyVar3

    SELECT s.stor_id

        , s.ord_num

        , s.ord_date

        , s.qty

        , s.payterms

        , s.title_id

    FROM dbo.sales s

        JOIN dbo.titleauthor ta ON s.title_id = ta.title_id and ta.au_id = @nMyVar2

    WHERE s.ord_date BETWEEN @dtMyVar3 and @dtMyVar4

    RETURN

END -- Procedure