problem in timer decrement in my application

[dhilipkumar]

I have problem in my project ,that is,

i want that time clock is reduced by a specific time suppose in filling the form in the  given time is alloted and after a specified time admin will block the form,

so i want that timer is decremented .

Suppose

aloted time is 01:00(hh:mm)

then time is shown as 00:59(hh:mm) ,00:58 ---like this and after 00:00 form is filled. So tell me how to do this in vb.net