Search Interface SPROC Design Question

I have the following layout for a search form: -

JobRef [TEXTBOX]     JobTitle[TEXTBOX]     Consultant[SELECT BOX]
                                                                               <option value="" selected="selected">All Consultants</option>
                                                      <option value="john">John</option>

Trying To Achieve The Following: -

1. Always Return records with STATUS = 'Live'

2. If Job Ref is input only one record is returned or none even with other combinations (JobTitle Or Consultant)

3. All other combinations are possible

JobTitle: -  job_title LIKE ('%'+@jobtitle +'%')

Consultant: - consultant = @consultant

If All Consultants are selected it will return all consultants records and filter if job title is inputted etc..

Query so far:  -

CREATE PROCEDURE spSelect_Jobs_On_Search
      @jobref            INT,
      @jobtitle      VARCHAR(100),
      @consultant      VARCHAR(50),
      @SortBy       VARCHAR(20),
      @SortAscending       CHAR(1)

As

-- Select Consultants For DropDown Box
SELECT  username,
      firstname,
      lastname
FROM Users
WHERE roles = 'Consultant'
ORDER BY firstname

SET NOCOUNT ON

IF @SortAscending = 'A'
      BEGIN
            SELECT      job_reference,
                  job_title,
                  dateadded,
                  status,
                  consultant
            FROM Jobs
            WHERE      status = 'Live'
            AND      consultant = @consultant
            AND         job_title LIKE ('%'+@jobtitle +'%')
            ORDER BY
                  CASE
                        WHEN @SortBy = 'jobref' Then job_reference
                        WHEN @SortBy = 'dateadded' Then dateadded
                  END
                  ASC
      END
ELSE
      BEGIN
            SELECT      job_reference,
                  job_title,
                  dateadded,
                  status,
                  consultant
            FROM Jobs
            WHERE      status = 'Live'
            AND      consultant = @consultant
            AND         job_title LIKE ('%'+@jobtitle +'%')

            ORDER BY
                  CASE
                        WHEN @SortBy = 'jobref' Then job_reference
                        WHEN @SortBy = 'dateadded' Then dateadded
                  END
                  DESC
      END

HELP !?

JT