Workflow event while updating USR02 & USH02

Hi Gurus,

We have a requirement to send mail notification & SMS (new password) to user , if user id has been locked due to failed attempts.

I have code to unlock user id & reset the password . But the requirement is to trigger this code when the USR02-UFLAG is set to 128.

Please suggest me with suitable enhancement places Or workflow events (if any).

Thanks,

Narendra.