Thx mr Eriksson for your quickley reaction
15 years ago i create 1 app in Delphi with foxpro as database
now i wil create this in VB.net and Sql Server
the prog is for employment registration with barcode
by scanning
the program must look or there is already a record with this date and Id,
Employe can leave company and comeback later on the day

now i explain the follow steps by registry
1] employe  146 scan at 16/11/2017 06:33:15
2] searching record with id 146 and date 16/11/2017
 if  found look to scanin
   if scanin IS NULL
     scanin = registrytime
   Else
    compare scanin  and registrytime
     if different between registry time and scanin > 3 minutes ---( security agains double registry)
       look at scanout
      If scanout IS NULL 
       scanout = registrytime
     Else
     compare scanout and registrytime
      if different between registry time and scanout > 5 minutes ---( security agains double registry)
      insert new record
Else -- record not found
   insert new record
-----------------------
The next step = calculate the working hours
I hope you understand the logic.
Thx almost mr Eriksson