selects RCtrials and MXtrials, such that the number of trials for each word position is balanced between conditions.

similar code is used to find trials for RConset and RCoffset. Each of these conditions has 3 word position.
RConset:  RConset-1, RConset, RConset+1, similarly for RCoffset
updated RCearlylate-MXearlylate and RConset-RCoffset. Code under these sections still need to be tweaked
Merge branch 'master' of github.com:schoffelen/MOUS