How to create a SQL Query with Between

Hi Allan, Thank for all your help.

I'm working with a Conditional query, and in my staff.php have this:

Editor::inst( $db, 'mknDetalleAseguradoras' )
    ->fields(
        Field::inst('FechaFactura'),
        Field::inst('Vendedor'),
        Field::inst('FolioFiscal'),
        Field::inst('CantidadMaterial')->validator( 'Validate::numeric' ),
        Field::inst('DenomMaterial'),
        Field::inst('ImportePiezaNeto')->validator( 'Validate::numeric' ),
        Field::inst('ReporteQualitas'),
        Field::inst('Interlocutor')->validator( 'Validate::numeric' ),
        Field::inst('Taller'),
        Field::inst('Poblacion'),
        )
        ->where('FechaFactura', '2014/07/10')
    ->process( $_POST )
    ->json();

But I need get a date value from $_POST for example:

$fecha = $value_get_by_post

$fecha_inicio = strtotime('-7day', strtotime($fecha));
$fecha_inicio = date('Y-m-d', $fecha_inicio);

And make this query:

->where('FechaFactura', '"BETWEEN ".$fecha_inicio." AND ".$fecha')

My question is: It's Possible, because I try the query but nothing happens.
I can define a normal SQL Query in the staff.php:

SELECT * FROM mknDetalleAseguradoras WHERE FechaFacura LIKE VALUE AND VALUE

Thanks in Advance Allan :D