setar main page with data from a popup

Good morning. I need help solving a problem. I have a page A where the application data is that I'm going to do. In the page a has a field that is the supplier but I opened a popup B. In the popup is made a query to the bank that returns the suppliers from the logged in user. in this list the user must choose a vendor and that vendor is inserted in the field on page A. can they help?