Lewis & Short

ad-quō, adv., i. q. the later quoad reversed, how far, as far as, as much as; only in two examples: iratus essem ad quo liceret, Afran. ap. Non. 76, 9 (Com. Rel. p. 196 Rib.): ut scire possis, ad quo te expediat loqui, Afran. l. l. (p. 200 Rib.); cf. Hand, Turs. I. p. 178.