How to replace a part of the filename in matlab or letswave docs?

I want to replace Mathlab and Letswaves doc names from avg ep S 71 icfilt ica EEchan reref but ep Part13_VA.lw6 where the EEchan needs to be changed in EEGchans. The 71 and the participant name will change. How do I do this, help

Best wishes, Elles

[Jan]

The question is very cryptic. You want what? Do you want to rename the files or to create strings only? What exactly is the pattern you want to replace? Is ths file name:

avg ep S 71 icfilt ica EEchan reref but ep Part13_VA.lw6

This would be really ugly. ;-) How are the file names stored? Which part is "the participant name"?