input function vs lookup field

input function vs lookup field

Hello, 
I have three forms (marked bold):

Customer
New task has a lookup field based on field from Customer. Then i have custom action which (among other things) creates record in Report:

  1. void VytvoritProtokol(date Do, date Od, string Uloha, string Technik, string Z_kazn_k, int recid)
  2. {
  3.     rec  =  New_task  [ID == input.recid];
  4.     rec.Protokol = true;
  5.     insert into Report
  6.     [
  7.         Added_User = zoho.loginuser
  8.         Koniec_z_sahu = input.Do
  9.         Kr_tky_popis_probl_mu = input.Uloha
  10.         Napl_novan_pr_chod = input.Od
  11.         Stav_z_sahu = "Vyriešené"
  12.         Technik = input.Technik
  13.         Z_kazn_k = xxxx
  14.     ]
  15. }
What should be instead of xxxx if i want there value chosen in lookup field (in New_task based on Customer)

Im finishing my simple application and im stuck at final step :(