hide and show customs fields based on interval between startdate and end date not match

[Oussama Dev]

Hello, 

i want hide costom fields (city and wilaya) when interval between two date (dateFin and dateDebut) is greater than 20d 

this is my code :

mainscript.sil

lfWatch("dateDebut", {"dateDebut", "dateFin"}, "path/controleDates.sil", {"change"});
lfWatch("dateFin", {"dateFin", "dateDebut"}, "path/controleDates.sil", {"change"});

controleDates.sil

date begin = dateDebut;
date end = dateFin;
interval intervalle = toRawWorkingInterval(end - begin,24);
if(intervalle > "20d"){

lfShow("city");
lfShow("wilaya");
}
else {
lfHide("city");
lfHide("wilaya");
}