Return edit distance for suggestions?

Hello,

It would be really useful in my application if it was possible to get  
the string edit distance (SED) for all of the suggestions returned by  
aspell.

Also, is it possible to alter the parameters of the string edit  
distance function? For instance, tweak the cost of swapping letters  
or inserting or deleting certain characters?

Currently I have my own implementation that lets me do this, but it  
seems like aspell is already doing a lot of this work in the process  
so i might as well not waste any time.

Thanks,
phil z