Quote: "will this interfere with the existing lighting"
probably not but i'm not sure (it probably depends what exactly are you going to do)
Quote: "Secondly I see that dbpro is using certain things such as "Object Number", "Mesh Number" etc. in their commands. Say I want to create a special texturing function within my dll which when called will apply a graphic image to a particular mesh or object in the scene.
Now my question is how do I tell the function on which object/mesh to apply the texture , because directx API won't understand object no/mesh no etc."
you can't use directx functions which operate on mesh basis because dx mesh and dbpro mesh are 2 different things. You can however convert dbpro mesh to dx mesh, aplly what you want and then convert it back.
As for textures, for proper texturing you will probably have to use dbpro built in functions for texturing limbs/objects. You can, of course, change texture pointer of already textured object
Quote: "To be more concise - how do I pass the object/mesh instance to the function as a parameter so that the function can work on that mesh/object ?
"
There is a function that takes object number as parameter and returns the pointer to the object structure that holds all the object data
