I use sort of an inefficient work around for this issue, but it's simple and it works. You just need to be able to keep track of it.
Use either CHARACTER_Player1 or - to be more safe - put in a dummy character and name it something like Variables, make it global.
Then I use CharacterSetVarInteger(CHARACTER, "Variable Name", VALUE).
These variables are unlimited, permanent, and can be checked at later times with "IF CharacterGetVarInteger", unlike global events which only fire one time and then are no longer able to trigger code.
Is it possible to add a number to an already existing variable or is it only possible to set it to a set value? Like in normal code you might write Y += 1 to add 1 to the already existing value of Y.