When displaying a number, I want to convert it from an integer to a string with leading zeros. Or something like that.

So I have an integer. Let's say 34. I want that number to be displayed as 0034. How would I accomplish this?

EDIT: I'm doing a countdown timer. I wan the timer to count down like this: 12, 11, 10, 09, 08, 07, 06......instead of 12, 11, 10, 9, 8, 7, 6, etc..... So it needs to be dynamically represented, not just adding two 0's to the string.