I don't believe the above solutions will work, but here's one that might: (Edit: Olipcs's solution might as well, it's a similar idea.)

/castsequence reset=16 [target=focustarget,harm,nodead] LB,LB,LB,,LB,LB,LB,,LB
/cast [target=MyNameHere] Chain Heal

So when it hits the empty comma, it SHOULD skip casting on that castsequence, allowing it to actually cast another spell later in the macro. The second line might have to be /castrandom instead of /cast, but I'd try the first one first.

Note that if you spam the button this won't work. If you do that, add a bunch more commas after the third and sixth LB.