ACL custom-fields IN CRS226

hi~
Is any one know how to use acl custom-fields ?(/ interface ethernet switch acl add custom-fields=)
There is no info in the Manual CRS features…Can some one give me an example?
I want to use the acl to redirect some packets,but I need more specific options.
I think the custom-fields is like the user define acl of Huawei that can mark any hex in any positon in the packet?