sprintf and justification\padding?

I'm trying to pad\justify my text such that everything aligns properly. Can I do this from within sprintf? I've tried all kinds of combinations within the format string.

Basically, this is the output I would like:

#001
#002
#003
....
#010
etc

unsigned char num;
unsigned char buf[20];

num = 0x01;

sprintf(&buf[0], "#%bU", num);