Record old passwords ?

[Tompkins Neil]

Hi

I'm in the process of designing a login system to a secure web page using
MySQL.  One of the features is we need to record and ensure that the user
password is different from any of the last four passwords he/she has used.
 I was thinking of create four fields called Password1, Password2, Password3
and Password4 to record the old passwords.

Is this a preferred method - or does anyone else have any recommendations ?

Thanks,
Neil