Yes, there is a vas.conf setting to do this. Here is the information from the vas.conf man page about the setting:
password-expiration-warning-message = <warning text>
Default value: Your password expires in %d days. Please change it as soon as possible.
This message is shown to users at login when their password will expire within the configurable password warning expiration window. A %d in the message will be replaced with the number of days until the password will expire.
password-expiration-warning-message = You must change your password in the next %d days.