request for remainder

Question

hi friends,

            actually I am doing a task management software for my self. and in that i need to be remembered by the system regarding the task to be done when that time matches as shown below table.
   * when the time is 10:00am on 30-dec-12 it has to show a remainder message regarding the task  irrespective of the work that we are doing in the computer ,similarly the other also...
 please help me in doing this ...

       

taskid	taskname	task details	remainder date	time
1	meeting	friends	30-Dec-12	10:00am
2	consulting	doctor	31-Dec-12	12.30pm