Hairline surgery to fix cowlick?

If posteriorly growing hair affects up to half your stable hairline, it would be very difficult to surgically correct it. If the unfavorably growing hairs are limited to a centimeter, excision might work followed at a later date with forward growing hair transplants. 

I am not sure which type of 'lick' you are talking about. There are frontal and crown licks. The classic Cow lick is in the crown and these are almost impossible to change.The ones in the front; however, can be changed with hair transplantation.