Use alias column in CONCAT expression

Question

Hi there,

 

I'm trying to use alias column  in concate expression but it is not allowing me to use directly,I have tried by using some solutions but ended up with some issues.

 

Can someone please suggest something on this.Here is my simple query.

 

SELECT DISTINCT scm_desc,
                CASE
                  WHEN email.subject NOT LIKE '%INC00%' THEN email.create_date
                  ELSE NULL
                END AS orgdate,
                CASE
                  WHEN tr_status = 'Closed' THEN
                  Concat(CONVERT(VARCHAR(5),
                         Datediff(s, orgdate,
                         tr_modified_on) / 86400)
                  , 'D',
                               '' + ':'
                               +
                  CONVERT(VARCHAR(5), Datediff(s,
                               orgdate,
                  tr_modified_on)%86400/3600), 'H', '' +
                                                   ':'
                                                    +
                  CONVERT(VARCHAR(5), Datediff(s, orgdate,
                  tr_modified_on)%3600/60), 'M')
                  ELSE ''
                END AS overdue
FROM   dbo.ims_transaction
       LEFT JOIN ims_mtr_sub_category
              ON ims_mtr_sub_category.scm_id = ims_transaction.tr_sub_category
       LEFT JOIN dbo.email
              ON email.incident_no = ims_transaction.tr_incident_no
WHERE  tr_status NOT IN( 'stu_CLS' )