initiate custom query from Search Page

Since there is no 'Save' button on Advanced Search page this approach most likely won't work.
My suggestion is to customize one of existing search fields instead of adding a totally custom listbox there. In this case you do not need extra buttons or custom WHERE clause.

Sergey,

Thanks for your reply. Could you help me further ? How should I customize one of the existing search fields to be succesful ? Would that be a dummy field being part of the initial table ? What steps need be taken ? Please help.
Yves

I don't quite understand what exactly you trying to achieve but yes, this can be a dummy field.
Dummy field can be added to SQL query as follows:

Just make sure this dummy field doesn't appear on Add/Edit pages as it cannot be updated.

Sergey,
I should have been more clearly at first :

What I am aiming at is this: instead of running the standard "SEARCH button" (was wrongly described as 'save button' in my first post, sorry for this) on the advanced Search page, I want to run a "custom search" through building a "custom query" to filter the initial _list.php. This could be fired from a 'custom button' for example. The custom query would have a WHERE clause reading "..WHERE fieldname1 IN (value1,value2,..) or fieldname2 IN (value1, value2,..) or ...".

The value list (value1,value2,..) will be fetched from the custom field (listbox) on the Search page. I have this listbox populated with the Javascript Onload event. What I do not know is how to build the custom query and how to tranfer the value(s) from the listbox to the custom query. The listbox value(s) read like (zipcode1, cityA, countyB,..) . Can you show me the right code ? Thanks for your help.
Yves

Sergey,
In the mean time I am getting step by step closer to my goal. Could you help me with this one ?

How could I mimick a 'Back to list' functionality by adding code to the 'client After'-event of a custom button on the advanced Search Page?
thank you.

Yves