Did you check out ramones' example? To me it sounds like it does everything you want except store the total time elapsed in milliseconds, is that correct?
If it is correct, just make another variable "t" like you have in your case, and instead of the "Set text to timer*1000" action in ramones' example, do "Set t to timer*1000". Now the "t" variable will hold the total amount of time elapsed in milliseconds, and the text will show the time in "min:sec:mill" with 2, 2 and 3 numbers respectively.