[SR-Users] modifying global data-structures using Rtimer module

Hi we have developed the custom module which stores the registered users in a file.now we are trying to remove the expired contacts using the rtimer module.while saving the registered users to the file we also store the expires values in static array.but when we try to decrement the these values in a function called with the help of rtimer module. the values used by this periodic function are not modified ones but the initial which are zero. is it that we cant pass the modified values of the global variables to the timed functions. to get around this problem, we also registered the timer in our module but got same results !!!!!!! Please Help. Thanks and regards .