From Creatures Wikia
Its argument or return value is relative to BASE if that is set.
Syntax: POSE sprite (integer)
Returns, as an integer, the current sprite being displayed by TARG/PART, or -1 if PART is not valid. If an ANIM is in progress this will still display the sprite being displayed.
Set pose to sprite 2:
Increment the current pose by 1:
setv va00 pose addv va00 1 pose va00