Creating a time without the pause function

How do I create a timer that counts down without using the pause function? It also asks the user for a positive number to countdown from and at the end it needs to display "Thank You"

disp('Welcome to the countdown timer program:');

done = false;

tic(); %start the MATLAB timer

while tic>0

time = input('Enter a time (seconds) or negative number to quit:');

time = input-1;

end

disp('Thank you');

end