Simulating a single scatter at an specified angle

Dear Fluka Experts.
I am puting a spectra into the code and like to find out how to simulate a single scattering event lets say at 180 degrees (backward). So I’ll be measuring the energy (loss) of the particle after the event.
Many thanks in advance,

Dear @MrPasgit,

Would you mind to elaborate more on the topic? What is exactly your question?