SQL Server 2008 :: Converting Job Duration From Job History And Use It On Email Notifications?

I am trying to convert the @runtime to hh/mm/ss format as it's currently printing milliseconds.

Declare @runtime varchar(100)
Select @runtime = sum(run_duration)
From msdb.dbo.sysjobs j
INNER JOIN msdb.dbo.sysjobhistory h ON j.job_id = h.job_id
where j.name = 'Accounts_From_App03'
and run_date = CONVERT(varchar(8), getdate(), 112)
Declare @Body varchar(100)
Set @Body = 'The Job completed successfully. Duration:' + @runtime

exec master.dbo.sp_SQLNotify 'App02@email.com', 'team@email.com', 'Scheduled Job Success' ,@Body