well there are different solutions for this: macro ones and software ones:

-for a simple macro-solution, you could simply add a '/click ActionButton7' to the macro on '6' so that after 6 is executed, 7 is clicked.

-for software solution with some KeyBroadcasters you could create a HotKey which presses both buttons simultanious (i'm thinking of HKN here, but IS and AHK should also work), but this maybe discussable, if it is ok with blizz (in my opinion, because no real 'waits' are used, for me it is, but I would advise people to do this on their own risk,because blizz might see it the other way...).