Trying to replicate a Radware load balancing setup - where a string is searched for in the HTTP header, then the following field (by offset) is used as the cookie.
There doesn't seem a way to do similar on ACE, the field is too far into the header to reliably find it by offset alone.
Have you tried type "generic"? For example:
sticky layer4-payload WHATEVER
layer4-payload yada yada yada
policy-map type loadbalance generic first-match LB-POLICY