Scancode to Ascii conversion?

I've started to code a simple GUI system, and stumbled across a minor
problem. I use Bitmap Fontbuilder from lmnopc software to create a texture
with all the ascii characters. and for normal english / US keyboards it
works fine, however, I use a Sedish keyboard, and would like ÅÄÖ to work
too, but they produce scancodes : 143, 142 and 153, but in the ascii texture
generated, they are around 250, so is there a simple (-ish) way of solving
this? And get the right ascii values from special characters.

Any help welcome.
//Martin