hi rick,
i see u don't have much experience with 8xC51 mcu's.
i'm willing to help u from time to time.
now there's a very interesting application note from intel titled "Designing with the 80C51BH".
the file's name is: ap252.pdf
try to find that file on the intel site, if u can't find it then i'll send it to u via email.
there's a section in that application note called "scanning a keyboard".
first u need to study that section on ur own and then if u still have questions about it then let me know,
but please be precise.
mourad