As you are using re framework i hope for each transaction you are getting one row
So add a new argument in_Transactionnumber
to process.xaml and link the variable from main which contains the transaction number value, after extracting the data you can use write cell activity and give cell range as "B" + i(n_TransactionNumber+1).ToString
This will ensure that the data is added for each row
Hope this helps
Cheers