Is there a way to format a string so that it is always left padded with zero's?

For example I have random set of number say: 1, 40, and 389.  I want to
always display the number 3 digits padded with zeros like:

001, 040, and 389.

I have the following code, and I am not sure if there is a way like C to do
this in .net:

int digit1 = 3, digit2=40;
string display;

display = string.Format( "[{0,2:3}] and [{1,2:3}]", digit1, digit2 );

the output for this is:  

"[  3] and [ 40]"

Its padded with spaces instead of zeros.  

I know I'm just missing something in the doc.  Anyone have any ideas?

~ trickytrini