Kill Session using Codeunit

With SQL Server you could also kill idle session with some TSQL:

use [master]
go
set statistics io off
set nocount on
go
declare @threshold datetime
set @threshold = dateadd(hour, -6, getdate())  -- threshold is 6 hours ago
print 'Killing processes which executed "Last Batch" before ' + convert(varchar(30), @threshold, 113)
print ''
declare @spid int, @last_batch datetime
declare spid_cur cursor for
  select [spid], [last_batch] from sysprocesses
  where [program_name] = 'Microsoft Business Solutions-Navision client'  -- change application name here
    and [last_batch] <= @threshold
open spid_cur    
fetch next from spid_cur into @spid, @last_batch
while @@fetch_status = 0 begin
  print 'Killing process ' + convert(varchar(5), @spid) + ', idle since ' + convert(varchar(30), @last_batch, 113)
  exec ('kill ' + @spid)
  fetch next from spid_cur into @spid, @last_batch
end
close spid_cur    
deallocate spid_cur    
go

This script searches for NAV processes which have executed the last batch 6 hours ago (please change the settings if applicable) and kills them. YOu could create a SQL Agent job which execute this script every hours.
If necessary you have to add some exception handling etc..

USE AT OWN RISK!