is it possible to exclude an object from receiving light and still cast shadow?

as the title suggests, is it possible for an object to not receive any illumination from a light source (direct light) and still cast shadows on other objects?
what i want to do is create a building on a site, i want to lightmap the building in an external application but for the rest of the site i want to use unity's realtime light/shadows. the only problem is the building is also receiving direct light, i can exclude its layer but then it will not cast shadows on the site.

 

Might be easier to just use something like this as a shadow caster.

http://answers.unity3d.com/questions/269292/having-an-invisible-object-that-casts-shadows.html

 

thanks for the fast reply antenna tree,
but if i use this method wouldnt i need another copy of the object since it will become invisible?

 

Yes, you need a duplicate that is used for the shadow caster.

 

thanks mate, looks like ill have to make a lowpoly duplicate object.