List products by custom field

hi. i'm creating an advanced search for products, and it involves search by custom fields.

i have custom fields like: number_of_rooms, number_of_floors, land_area, etc.

is there a way to display only products whose "number_of_rooms" is equivalent to "5" ?

i don't see how i can use "mp_list_products" to accomplish what i need.
i was hoping i could use something like: mp_list_products(true,true,1,$ppage,$field,$order,$custom_code);
$ppage -- items per page
$field -- order by
$order -- sort by
$custom_code -- number_of_rooms=5&number_of_floors=2&land_area=250