Doing summarization task with dialog buttons

Hi. I found this code here and tried to utilize it in one of my tasks.I want the user select two fields to see for example how many different companies have the same IBAN numbers by doing summarization task. So, the user needs to first choose IBAN, then needs to choose the company. Here actually I want to detect that these companies' names are failed to be saved previously.
I am completely new to this program and ready to take all the advice and help. Thanks in advance!