When I looked into buying mine this year, I read through the online instructions and configurator and they stressed the importance of a C connection. I didn't see anything about certain functions that may not work without it, but it was plain that the battery would drain quickly without it.
Taking your 'handle' literally, it's not hard to pull a new cable. Home Depot has 4, 5, 6, 7 and 8 wire thermostat wire bundles. I just wrote down my colors and terminal letters, disconnected it at the furnace and tied the old and new ends together and pulled it through. I just matched up the colors and terminals again at both ends and was all set. You're screwed if they stapled the wire to the studs inside the walls, of course. But I've never seen that done.
And if you have trouble finding a terminal on the furnace board labelled C (mine was actually labelled B) just look for a 2 wire bundle that runs outside to your A/C compressor. One of those wires will go to Y and the other wire will be your C connection. You'll end up with 2 wires connected to Y and 2 wires connected to C and one wire connected to the other terminals when you're done.
