CENTER(s,length[,pad])  or  CENTRE(s,length[,pad])

This function returns a string of the given length containing s. If s
contains fewer than the required number of characters, then pad
characters (pad, or by default, blanks) are added on each side to
centre s in the result, otherwise characters are taken away from each
side of s leaving the middle block of characters. If an odd number of
characters needs to be added or taken away, then the right-hand side
loses or gains one more than the left.