Resto Shaman macro.

Is.....Is there a way, to macro a key, which is repeatedly spammed, to refresh a Heal Over Time, ONLY....when the HOT drop off the target?

My example.

Running with a ele sham & warlock crew. Both the ele's and the lock have spammable cast macros. Yep, bound to the same key...just mash it and they dps...

I was hoping, there was a way, that on the resto sham, I could use the same key, to cast Riptide. However, when repeatedly spammed, the riptide spell will refresh every six seconds.
This wastes a heap of mana of course and you are only getting about 33% of the spell....

So is there a way that I can make a macro:

/cast Riptide
(then blank out the key so it cannot be used for 14 seconds) Kind of on its own global cooldown.
Or even a castsequence that has a 14 seconds gap between casts.

Is this possible? or am I pipedreaming?