font rendering and transparency

hello, Is there any way to make the black parts of a 24bit texture completely transparent ? I can''t seem to save 32bit font textures so i have to use 24bit. Other than applying the alpha manually when the texture is loaded (if (rgb == 0) a = 0). I''m using bitmap font builder to create the texture but when I save as 32bit it comes up all white, regardless of background/foreground colours. cheers, rich