The IDS sensors do not use ACLs to do blocking on the Pix. (Unlike routers where the IDS creates ACLs)
Instead the Pix has a special command put in specifically for blocking with an IDS sensor.
That command is the "shun" command, and is available directly in the Pix CLI.
The "shun" command is not specific to an interface of the Pix, instead the Pix automatically applies it to all interfaces.
SO you just need to enter the Pix login information and do not need to enter any information about any of the interfaces.
You can execute "show shun" on the Pix to see what addresses that the IDS is currently shunning on the Pix.
NOTE: You need to run a version of the Pix that has this "shun" command in it.