Tool for tracking time between follow and unfollow in Twitter?

I’ve been asked to manage the twitter accounts for a couple of local charities.

They all already have 100+ followers, but things have stagnated. I would like to find a way to follow accounts and then come back again after a week or so and – if we have not been followed back – unfollow these accounts.

I’m hoping there is a tool or something that will allow me to do this without having to make a manual list of follows and then consult this again in a week or so to unfollow. The charities have quite a few accounts they want to follow that they know will never follow them back, so I don’t want to unfollow everyone who isn’t following back, just the new accounts I’m starting to follow going forward.

Thanks.