Hello! I work as a senior testing engineer at top 1 bank in Russia and I write tests using Java, Selenium and Cucumber. So I will be happy to help you.
I can make script for you with С# and selenium. It will be exe file with txt file. You will need to set data (logins, passwords, user names) to txt file and run exe after that firefox browser starts and do all work.
Hope to hear from you soon!
BR,
Ivan