Set And Start Timer When Input Value And Click Button?

i am trying to set up and start the timer for few seconds when I input the timer seconds value in the textbox and click the button, wait for the timer to countdown then show up the messagebox. [code]When I input the timer value in the textbox and I have clicked the button, it did not start the timer for a few seconds which it show the messagebox straight away! How do i start the timer for a few seconds by input the value in the textbox and click the button then wait for few seconds while the timer start to countdown then show the messagebox??