In memory channel programming for the FT-70, you find an option PR FREQ.  This option works in conjunction with the Tone Mode setting PR Freq. 

This option turns on a REVERSE CTCSS Decoder.  Notice I said REVERSE.  This option BLOCKS an incoming signal that carries the selected PR Freq and allows all other signals to be heard. 

Use with care. You could end up missing the call from someone you want to hear and hearing everyone else!!  

Note:  We suspect this is the same functionality of User CTCSS seen in other Yaesu radios.  We have not had a chance to investigate the manuals.  You might want to before you try using that option for something "special".