Yes, that's what I ended up doing actually 
One global variable called trBackupUnixLastRun that runs at the end of the macro.
Then at the top of the macro I have this:
I was having an issue with the UNIX time not being accurate, but for this particular scenario that doesn't matter, because all I want is the number of minutes in between them
I didn't know this was the right term for this. Always learning. Thanks!