Rebinding one-half of a key?

Hey /prog/ I want to rebind my parentheses keys to my square brackets keys, but I don't know how to rebind just my parentheses and not the 9 and 0 keys as well, as all the programs I have found rebind the whole key, not just half.

I remade the whole layout, parens are unshifted.

Learn to use xmodmap, if you're using X.