I'm not sure if this will work but I'm trying to tag an answer onto an old question from a year ago, will copying the subject line from that query achieve that? The original query can be found here: http://comments.gmane.org/gmane.science.biology.informatics.conductor/ 39289 I did not see a resolution to a problem with a RemoveProbes probes function for affy cdf kindly provided by Ariel Chernomoretz. The function was failing with the error cannot change value of locked binding for 'hgu133plus2probe' I found that adding the line unlockBinding(probepackagename,as.environment(ipos)) before the line assign(probepackagename,probe.env.orig[-iNA,],pos=ipos) corrected the issue. Thanks Elliott