JMeter IF-condition check

In client-side script 1st user creates events in a calendar for 2nd user, 2nd user accepts/declines them.

I would like to exclude possible errors during event creation and check if event request was created before 2nd user tries to accept it using xpath built on event request template like:

EventRequest_SubjectN
(N is iteration number of event request in a cycle, so if event request N wasn't created by 1st user, 2nd user action with event N fails).

Between these actions are another actions of both users, by this reason I can't use ${JMeterThread.last_sample_ok}.

Is there any analog of this function, but for necessary/specific action several steps ago, not for last sample?

What is the best way to organize IF-condition is that case?

I think about to add BeanShell PostProcessor after 1st user Event request N with a code like:

var rc = prev.getResponseCode(); if(rc.equals("200")){

vars.put(${_V(EventRequest_Subject${N})}, "${_V(EventRequest_Subject${N})}"); }

and use not null condition for ${_V(EventRequest_Subject${N})} in IF-controller for 2nd user.

But it doesn't work in this way. Where am I wrong?