Apply WHERE also on the search fields and when adding a row

Hi all,
I have a table where I only show specific rows depending on specific column values.

For this, I use $crud->where(…) and it works well, since the datagrid only shows rows compliant with the WHERE condition.
My code in the controller is something like this and works well for the datagrid:

	$crud = $this->_getGroceryCrudEnterprise();

	$output = $crud->render();

Now, I would like to achieve the same also on the related column search of FIELD_1, and in the related FIELD_1 when I click on the add form.

For example, if all FIELD_1 values are 0,1,2,3,4,5 and the WHERE range is 3,4, I need the FIELD_1 search only to show 3,4. The same when I click on add item.

How to do it? If using callbacks, could you please provide a short example?