Prioritize Attack

Lazy Macros How To's
1

Would like to prioritize attack for example

/castsequence overpower, mortal strike

if overpower is avail cast it if not mortal strike? how would i lay this out?

2

For example

/castsequence overpower, mortal strike

It will mortal strike if overpower isnt available, or will overpower if avail first then mortal strike?