Question regarding the fill function.

I was wondering how to use the fill function to place leading 0's before my integer value, provided it's not of a certain size. In the program I'm writing, I'm supposed to accept a membership card number. This number can be between 1 and 999999 inclusive. The formatting is supposed to be 12-3456, but whenever the number is less than 6 digits long, the format is 00-0234, etc. I was trying to use the fill function to do so, with no luck. I've separated the number into two integers representing the first two digits and the last four, I just can't seem to get the leading zeroes. Any ideas?

- Chris