If I understand correctly, you are wanting to have it so that your game/app loads the model and texture from their respective locations(In your example from two separate folders), and have the texture applied to the model. This is quite simple, as long as you have your model already UV mapped, and know the relative path to the items.
First you would load up the model, normally you would have just the name of the model, but since you want to use a folder structure, you have to put the path as well. In your case it would look something like this:
dbLoadObject("DATA/Models/
modelnamehere.x", object_ID);
next you would load your texture, this is the same as loading your model:
dbLoadImage("DATA/Textures/
texturenamehere.bmp", texture_ID);
finally all you would need to do is call the texturing command:
dbTextureObject(object_ID, texture_ID);
and that should work, if I am not mistaken.
If you don't want to worry about doing all of that, my suggestion
if you are using .x files would be to actually edit the texture file name part in the file itself. This is easier than it sounds. Simply open up the file in a text editor (ie: notepad) and find the item tagged as "TextureFileName", a simple ctrl-f and typing in texture would do the trick. next change the name of the file to the relative path, in this case:
from this: "
filename.bmp"
to this: "../Textures/
filename.bmp"
the two dots represent going to the parent folder (the one before the current folder).
Hope that helps
-H