Configure a capture on the inside for this specific host that uses that trading application to the tradig server, something like:
access-list capture permit ip host (client) host (server)
capture cap access-list capture interface inside
Then ask the user to try to connect to this application then after this application works go ahead and do a "show capture cap" which will tell you what destination ports is this client looking for, then you can open those on the acl.
Or simply take off the inside acl, ask the client to connect and do a show conn detail and check which is the destination port.