As i alluded earlier, one way is to have one master loop which consists of calls to perform specific processing at certain frequencies.
i.e.
loop start
tick ++
if (tick%2) then move missile
if (tick%100) then update health
etc
end loop.
I posted how to do it above. Twice.
The code Nate posted is the same way I do it.
One small correction
fireTimer -= fireTimer;
should read
fireTimer -= delta;
Oops! Good catch. 
Yes I notice that now Nate. sorry, but i didnt quite understand what was happening in the code you posted, so that why I asked about it again.