Debug printer install powershell GUI

I am working on a powershell gui to install network printers. I currently have a working script that has a single server hard coded into the script. It displays the shared printers from that server in a listbox. you can select the printer you want and install it and set it as default if you choose. I am attempting to improve the script by adding a dropdown that includes other servers. the issue I am having is populating the listbox from the selection mabe in the dropdown.