How to modify "resources.assets" (or alternative?)

Hi, is there any way to add/remove files to/from the resources.assets file?

I would like to load prefabs from external resources during runtime. Of course I thought about AssetBundles, but unfortunately I can't afford Unity Pro.

I thought I could achieve this with Resources.Load() until I noticed that I can't just put files into the "Resources" folder and load them after building the game.

Maybe there is another very different approach that I don't know?

Thanks in advance!

EDIT: I found an ugly and complicated yet possible method to "inject" external assets in the game. In the game I create, for example, one main scene and 50 empty scenes and then build the game. If I now have (from another unity project) one empty scene (as the first) and (as the second) a scene containing the assets I want to load in my game I can build this project and get two important files: level0 and sharedassets1.assets (must be at least two scenes in order to get the level0 file). I can now replace one of the empty scenes in the game with these files and load their contents with Application.LoadLevelAdditive(), so the point is: Scene = AssetBundle! Maybe it is helpful for someone, for me it works.