Ok so lemme see if I'm understanding the situation correctly up til now... There are several objects with a variable, each one has a different (changing) value assigned to this variable, and you need the sum of all these individual values?
Perhaps this could be done with a For Each loop, though I probably wouldn't assign it to Every Tick anymore because it might slow down performance. So it could look something like this:
(Assume global variable is used for the total sum)
Every 5 sec -> set Global Variable to 0
[sub event] For each Object -> add object's variable to Global Variable
This should tally the variable of every individual object, and the global variable should be set to 0 to avoid stacking old values with new ones.