Stop our clients from altering their password for a short time

I would like to inquire whether it is possible for us to stop our clients from altering their password for a short time. This is because we want to carry out some backup analysis and for this reason we would like to disable our network but not make any alterations or amendments to the passwords.
This is why we would like to know for the time being if we can stop our clients from changing their access codes.
