yes i think this can be done, i don't do it but i have seen messages that people get it done but with low volume.
so you might be better off to use another wav editor program to record your microphone when you sing,
then you can put that wav file in to your kfn file when you make the kfn file if you want to use it for
the training track in the file.
or if you just want to have a wav of you singing then you can just save it in that wav editor and play it when you want to hear it.
there is a good free one out there. called audacity it has tons of options and features with it. and there is another one called Wavosaur Wave Editor at wavosaur.com but that is like the old style it records and saves in ram. the audacity records and saves in small 3 or 5 second tracks in the temp folder so you have use of all the ram you got on your system, and can go for hours or until your page file gets filled up. then it will crash audacity
but audacity is also a little eaiser to use for the newbies it has plugins like wavosaur but they have a better gui then wavosaur does. better by easier to work with.
