Rotate Lisp

We have 3D isometric drawings that I want to place flow arrows on. Below is my code but it's not doing the "rotate, reference" correctly half the time. Why would this be? The Block I have coming in is initially set facing to the right, then I just need to rotate it to reference the two points that the user just clicked:

(defun c:flow (/)
   (command "pspace")
   (setq pt1 (getpoint "\nPick First Point:"))
   (setq pt2 (getpoint "\nPick End Point (direction of flow):"))
   (command "-insert" "Flow Arrow" pt1 "" "" "")
   (command "rotate" "last" "" pt1 "R" pt1 "@.75,0" pt2)
   (command "move" "last" "" pt1 "@0,-.5")
   (command "chspace" "last" "" "pspace")
 (princ)
)

Any help appreciated.

Thanks!

Through searching other sites I have found the answer. Below is the modified code if anyone else has the same issue.

(command "rotate" "last" "" pt1 "R" "@" pt1 pt2)