so insread of firing off SS it will do Ambush instead?
No, that would be an automation thing which is not a supported thing in a macro.
Can you only use it when it proc? If so You could try putting ambush on a separate macro and then put that one in the key press of what ever one your using then it will keep trying to press it so when it does proc it will go off
look at my macro. posted spleen
not exactly what you want but this is good /cast [stance:1/2/3] ambush