Stopping a Timer With Virtual Keys

[zb0S216C]

I've created a basic window which handles virtual keys. The case VK_UP initializes a timer which is counting from 9 backwards. The timer can be stopped if either 0 is reached or VK_DOWN is pressed. The problem is, when I initialize the timer with VK_UP the program stops until the timer has reached 0. How can I interrupt( stop ) the timer with VK_DOWN?

[guestgulkan]

what does this timer code look like??

[zb0S216C]

Same as this one: http://www.cplusplus.com/reference/clibrary/ctime/clock/