CO2 regulators

Whenever the pressure in my keg is higher than what the regulator is set at (for example when dropping the regulator setting from carbonating pressure to dispensing pressure) if I don't remember to release the pressure from the keg first, beer backs up into the regulator through the gas line. I know this has to be bad for the regulator. Is there a one-way valve of some kind that could be placed in the tubing connecting the regulator to the keg that would prevent this from happening?
Thanks

You can put a check valve in the line.  I have never had this problem.  How long is your gas inlet tube - it should only be an inch or so long and should not be immersed in you beer.

Thanks DaveinPa,
I'll have to look for a check valve that is the appropriate size for the gas tubing (5/16" ID?). I should have mentioned (Duh) that last year I switched out the gas inlet tube in my keg to a long tube that goes all the way to the bottom of the keg and has an aerating stone on it. I've found that this speeds up the carbonating process significantly (the batch will carbonate in a day or two without any shaking of the keg).

Ok, that explains it.  You can measure your tubing with a bolt - if its the right size it should just fit.  Amazon has polypropylene check valves in small sizes.