i've been challenged to write an app simulating keystrokes. After pressing shortcut app should be able to send predefined key combination to currently active app. It is functionality provided by many existing applications, but i want to write it on my own. App should be usable on windows.

Could you provide me with suggestions about:

1. which programming language should I choose?
2. Is there any libraries providing such functionality?

EDIT: To be precise: both applications are standalone, windows app.