Reading input cycles.

Can anyone explain to me or tell me if it is even possible to read the input
cycles of the line power into my computer using visual basic. I would like
to be able to write code to trigger something at every cycle peak or maybe
every other cycle or any other division...Maybe even once ever 60 cycles.
Can anyone shed some light on this. I have vb6...I would like to use my
parallel port...I can handle that end of it....

Thanks in advance for any help on this...Chip