Sorry i was mistaken, the event is called from a programatic change event.
There are two forms, one to search in and one to show details about the found record in the search form.

The search form puts a nID_number in a textbox.value on the detail form.
The programaticChange event from the textbox refreshes the form.

For example, in the searchform you can look up the name of a person. The detailsform shows the details about this name (triggerd by the programaticchange event).

The listbox is going to be used to list all contacts of this person.

I'm afraid the techniques used (above) are not my choice.
To throw the thing out and start over isn't an option. (yet)