SQL Syntax help

Hello,

I need some help modifying this query.

I need the syntax to display the time difference between ProcessStop and ProcessStart in minutes. The alias for this can be called ElaspedTime. I also only need to display records that have an ElaspedTime of 10 minutes or less.

How should the code look?

Thanks.
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SELECT     cli_procid AS 'ProcessID',
                          (SELECT     RTRIM(proc_start_date) + ' ' + RTRIM(proc_start_time) AS Expr1
                            FROM          ProcessID
                            WHERE      (proc_id_num = b.cli_procid) AND (proc_step_num = dbo.fnGetFirstStep(b.cli_arnum, b.cli_appl, b.cli_sub_appl))) AS 'ProcessStart',
                          (SELECT     RTRIM(proc_end_date) + ' ' + RTRIM(proc_end_time) AS Expr1
                            FROM          ProcessID AS ProcessID_2
                            WHERE      (proc_id_num = b.cli_procid) AND (proc_step_num = dbo.fnGetLastStep(b.cli_arnum, b.cli_appl, b.cli_sub_appl))) AS 'ProcessStop',
                          (SELECT     MAX(proc_count) AS Expr1
                            FROM          ProcessID AS ProcessID_1
                            WHERE      (proc_id_num = b.cli_procid)) AS 'TotalCount'

FROM         ClientDataFiles AS b
WHERE     (cli_arnum = '111111')