Maybe you can do it the other way around, let Playmaker get the variable, and if needed write into the Globals (probably not needed when you already have it in the script and can get it when needed. You can use Get Property, or probably better, add your own (simple) custom action. To do this most conveniently, find the custom action wizard tool in the top menu under Playmaker, somewhere in there. MDotStrange in the forum and on YouTube has a simple good explanation on how to write such simple get/set variable actions for your purposes.
Btw, you can write if(aim), which is the same as if (aim == true). False is if (!aim). Also, you should use a bool for the aim as well, rather than 0/1 as off/on.