yes you can with a relay, however will need to set two switches ( then two relays at least ), one for parkings circuit ( which will feed also the wheel dimmer function if you will use it, for cluster lights ) then another one for headlights. You could in fact use just one relay into the green wire for headlights and still keep the floor dimmer switch and won't need any other relay. Any relay is able to handle that load and floor dimmer switch is a rough switch to also handle the loads sucked by the headlights even being halogens.
We tipically use dual relays, one for low beams and another one for high beams just because tipically everybody install these into the engine bay after all the old, dusty, rusty, dirty contacts and switches and these are separated into a dual circuit, but one relay could be also used before the dimmer swith to handle both circuits... as far contacts are clean and dimmer floor switch is also in good conditions to assure a good power path. I have my relays just right after the floor dimmer switch into the cab, before the bulkhead terminals, and I'm using halogens and everything is perfect with them.
