You save a real value () in a hashtable, using the key of a unit as 2nd value and a nubmer you like (e.g. 0 = unit, 2=real, 35 = location.... I'll use 0 as example).
You add your unit/destructible/whatever to a group.
Now, check with a periodic event every unit/whatever in the unit group. (like every 0.1 seconds)
hashtable -save real: arithmitic(load 0 of key(picked xyz) of examplehash -(whatever you want to decrease, in my example 0.1) in 0 of key (picked xyz) in examplehash).
if (0 of key (picked xyz) in examplehash is equal or less then 0)
then do - actions
remove xyz from group
clear all childs of key (xyz) in examplehash
whatever you want to happen as the actual actions
You can access all amount of data via the hashtable (units, regions, flying height, integer, .... you get it
), at the same time you get to check every affected unit via periodic event pick units in unit group
both are 'linked' together by the key of a unit you've used to save stuff in ^^
Is that a bit clearer or shall I rephrase it?