How to use if-else

fin.xaml (18.1 Kb)ASIN.xlsx (11.2 KB)
i have uploaded the project and excel file… now how should i check for the presence of upc number on the first website holidayrush.com and if not found then search in another website and then copy the same upc number from website back to excel file. Can u help me with it?? thank u in advance.