The only risks for HIV in adults are:
1) Having unprotected anal or vaginal sex, or
2) sharing intravenous needles with IV drug users.
Nothing else you can think of, including this activity, is a risk for HIV. There is no "what if" that you could add to this event that would make it a risk for HIV.
I'm a man doing handjob using other people's sperm. It can be said that we masturbate using each other's sperm.