Painting a bump map with texture paint mode (and see bumps, not grayscale)

Hi,

Using GLSL mode, is there a way I can paint a bump map on a model using the texture paint, but rather than see the grayscale bump map, I’d like to see the results of the bump map. Unfortunately, GLSL only supports tangent-space normals (at least as far as I know!)

Anybody know how I can go about doing this?