[Eru]

Cast FS
Wait For Target
Exec: Last Target.

that hard?

Thats much about it. And on the "Wait for target" change the timeout to 1.

Or for a little more speed, turn on target queuing, then:

Exec: Last Target.
Cast FS

-edit-
Also, I can understand someone who has a lot of nice macros who doesn't want to give them away. If everyone has them, then they don't become as effective, and if you post all your best stuff, everyone knows that you use and a bit about how you think during PVP, etc. Plus, if someone else has other, better macros that they aren't sharing, then that other person is now at the advantage since they aren't sharing theirs.