Are there anti-greenhouse gases?
Fundamentally your reasoning is flawed because the major composition of the atmosphere is nitrogen and oxygen.  "Pumping a few parts-per-million" of some other gas into the atmosphere won't do anything to the relative contribution of GHGs to global warming.  GHG's contributions will still be felt the same, regardless of the presence of any other gas.  The "anti-greenhouse gas" that you refer does not exist.  All gases scatter and absorb different wavelengths of light in unique ways, and this all varies by temperature. However, no gas destroys light energy.  A realistic answer is to increase clouds and aerosols, which will reflect more energy back to space before it can be absorbed by the Earth's surface.  

Humans now account for the majority of greenhouse gases in our atmosphere.  Regardless if we shut off all our GHG emissions, our climate will still be warm for at least the next century.  Realistic solutions to reduce climate warming include:


grow massive tree farms; increase algae production and forest cover.
stop emission sources
cover disturbed and urban surfaces (and rooftops) in reflective color/material
cloud-seeding (which can also increase snow-cover)
Injecting aerosols/particles into the stratosphere to mimic a major volcanic event