Problem in Facing Changing the Password using Visual Webpart

Are you looking for a way to Change the Password using Visual Webpart ? then read this thread to know how to change it

I Have A visual web-part of changing a password of team site(it automatically changes the password in Active directory but it is taking 3 min time to update the Active Directory in the mean time user can able to log in into both the password new one and the old one )
1)so how to reduce the time interval
2)else is their any way to update password in active-directory
3) Or how can i handle these time period(what i mean to say is shall i lock the account up to new password is updated..? is it possible..?)