block filter driver

hi

 i want to write a blockfilter driver actually it tracks the each read
and write to the disk block .. take the disk block as 4k .. where each
sector is 4k...and it also has to mark the changed block .. and i will
get request from the server asking to send the changed block only...
before this i have to take the full image of the disk and send it to
the server..afterwards it has to find any chages made to the disk and
mark which block got changed and raed the those disk block only and
send to server .. plz help me ..