[Cmake] conditions based on cmake version

[Wheeler, Frederick W (Research)]

Is there a way to use WRITE_FILE() if and only if it is supported by the
version of cmake in use?  Something like this?  I'm just guessing at the
version here.

IF( CMAKE_VERSION > 1.6.1 )
  WRITE_FILE( ... )
ENDIF( CMAKE_VERSION > 1.6.1 )

Does anyone have a quick example of this?

Thanks,
Fred Wheeler