I have created a video guide for Assassination and how to set up the macros for those who need a little help.
Here are the macros. One is for building CP and the other is for spending CP. (NOTE: Slice and Dice should be on a button by itself or you could add it in the macro with a modifier.)
Combo Point Builder:
#showtooltip Mutilate /cast [nostealth,nocombat]Stealth /cast [stealth]Ambush /castsequence reset=0.3 0,0,0,Vendetta /castsequence reset=0.3 0,0,Mutilate /castsequence reset=0.3 0,Dispatch /cast Shadow Blades /startattack
Combo Point Spender:
#showtooltip /castsequence reset=target Rupture,Envenom,Envenom