Some thoughts/ideas
First thing you'll need to consider is that CATV cable is 75 ohms as most coax for communications use is 50 ohms. Scanner antenna inputs are 50 ohms. You'll need to figure out how to compensate for the impedance mismatch at both ends. Some sort of impedance transformer (75>50 ohms) should do the trick.
I don't know what you mean by a "control box". In a typical CATV house cableling (assuming more than one outlet), from the drop outside before the cable enters the house, there should be a splitter. The output ports on that splitter have inherant losses. If there are more splitters beyond that first, the losses add up.
If you can figure out which cable runs to your office from the splitter outside, you can replace the splitter with a barrel connector.
As for as length of run is concerned, I don't think you'll have a problem as long as you can solve the impedance issue and there are no more splitters between your office and the outside. You can find out for sure by checking the cableling inside from where your office cable fishes through the wall to either the attic or basement/crawlspace on its way to the outside.
If you're willing to get dirty, I say go for it! That's what experimentation is all about!
