How to use an OR statement in a Post-Build event?

I am trying to use a conditional with an OR in a Post-Build event, but so far, I have had not luck. The following does not work:

if not "$(ConfigurationName)" == "Debug" or not "$(ConfigurationName)" == "Release" (

but this works:

if not "$(ConfigurationName)" == "Debug" (

With the first one, I get an exist code 4.