I know what it is! I wrote /cast instead of /target. It needs to be /target.
The mouseover line in the macro should look like this:
/click [button:2] DUNG RightButton; [button:3] DUNG MiddleButton; [button:4] DUNG Button4; [button:5] DUNG Button5; DUNG
Mouseover feature is definitely important as it makes all the difference. Please let me know if it works now.