invoking custom validator

I want to know this:

while I am within a script handling an event (onBlur), is it possible for me
to trigger a different event on another control, say a custonm
validator control? If so, how? May I have an example, please.

Here is more information: what i am basically trying to do is to set
IsValid=false of a custom validator, BUT based on
conditions determined while handling a different event.
Any help would be appreciated.

Levi
llevil (AT) optonline (DOT) net