comparing variables using logic- need help

I have got two math counters in my map. One is counting BLU score and the other RED score. I also have a round timer entity, and I want to use it, so that when the timer will end, the two math_counter's values will be compared.

I thought of using a logic_compare to do that, but it seems like it can only compare "real" numbers, and not variables, like the ones in the math_counters.
How can I compare two variables in source?

Thanks, I didn't know about the outvalue and setvalue I/Os.