Equivalent of trigger and stored procedure in MySQL V4

[Dabbsy]

I'm running MySQL V4, and whenever a row is updated or inserted into a table, I would like to be able to do various checks and calculations, and then based on that, certain row manipulation for other entries. Triggers and stored procedures would be ideal, but I believe they're only around at V5 (client doesn't want to upgrade right now). Has anyone any ideas (I'm very new to MySQL but have plenty of DBA experience)?
Thanks in advance

[zCat]

Upgrade to version 5? Below that your only hope is to do whatever you want to do on the application side.

Personally I've given up on MySQL for all but the simplest of tasks, and use PostgreSQL for "real" database stuff (including high-performance web backends).