Calculation - find middle of a string
I have a field called ID_EVENT witch has values like ABCD-DOC-2012-0001 or ABCD-AUDIO-2013-00004
I need to add another field called FOLDER_TYPE witch would be filled with DOC or AUDIO depending the case of the field ID_EVENT of that record.
I already have more than 2000 records, so my question is how can I do it at once?
Is a calculation the best way? I thought so, but I stuggled to do the find.
Thanks in advance for the help