Can a reactor be operated at both reflux and above atmospheric pressure? I'm not a chemist by trade so my experience in the lab has probably not been as in-depth as most of you. I've been tasked with investigating a proposed reaction in which an organic mixture (mostly formic acid) is to be heated at reflux for several hours.

The complication being that a pressure of approx. 4 bar is required during the reaction. How would one go about achieving this? The reflux condensors I've browsed through are all open to atmosphere on one end.

Is there some sort of pressure regulator I can attach on the output of the condensor to maintain the pressure at 4 bar? 

I'm told that the reaction may produce $\ce{CO2}$ and $\ce{NH3}$ by-products which means pressure is expected to increase and fluctuate as the reaction proceeds. Ideally I'd like to occasionally vent these to drive the reaction equilibrium forward.

The formic acid is quite corrosive to anything not plastic or glass.
You could theoretically boil at the higher temperature but why would that be a requirement? Why would you require reflux specifically if you can actually heat the formic acid to higher temperatures under pressure? Heating should work on its own and degassing to drive the equilibrium should work with a back pressure regulator. However,  most lab glassware will not take that pressure. You normally need some stainless steel pressure equipment. 
One way might be to use plug flow reactors rather than bombs.