[AccessD] A2K: Stop User from oving to new record

Hello all
In relation to stopping a person moving to another record before the previous one is complete...
I put some validation rules on the table. Now it's working fine.....almost

Does anyone know the err number Access throws up when table level validation is not met?
If anyone does know, how do I trap it at form level and throw up my own message box?

Many thanks

Darren