Is a batch import of usernames from Excel possible?

Please can someone advise if what I want to do is possible? I’ve raked around the codex but I don’t really have much of a clue about SQL, so I’m kind of in the dark here and would really appreciate some advice.

I run a WP site for my work which is used by 3,000 members of staff. At the moment the site is completely public (sorry, don’t want to give URL as it’s work-related).

I want to give these 3,000 employees individual usernames so they’ll be able to log in with “subscribe” access and view restricted posts which are not viewable by the outside world.

Each employee has a unique staff number, and I hold their names and numbers in a big Excel spreadsheet.

What I’d like to know is, is there any way I can import all these names and numbers into WordPress so the employees don’t have to physically subscribe themselves on an individual basis?

I’d like to set them up with their own unique staff numbers as their usernames, and just set one password which I will then change on a quarterly basis. (The restricted posts are not hyper-hyper-sensitive so I don’t need the most watertight of security here.)

So I’d send an email out to all 3,000 members of staff saying “Your username to view restricted posts is your staff number, and XYZ is the password for the next threem months”.

I just need to know if I can import all this data in a batch rather than me setting up 3,000 users by hand!

Any advice would be brilliant and much appreciated.

Kind regards,
Croila