So, I want a macro that pops trinkets, icy veins and elemental when available - and otherwise just spams frostbolt - Is that even possible?

Or do I have to do a click macro and get the timing right?

Was hoping that this would do the trick:
/use 13
/use 14
/click BT4Button73
/castsequence Icy Veins,Summon Water Elemental

the click is just a /cast frostbolt