To add a variable to an existing REC file, I tried what was discussed on:
http://lists.umanitoba.ca/mailman/htdig/epidata-list/2010q2/001427.html
But I didn't have it very clear. I finally made it doing the following steps (using EpiData 3.1, under Microsoft Windows):
1) Editing the QES adding a variable with a temporally name as "new".
2) Then, Tools -> Revise Data File
3) Tools -> Rename Fields
4) I go to the new variable and then edited the subsecuent variables with a temporally name also. The added variable should finally have the name 'P1103e' and the subsecuent variables must be "moved". In that sense the new variable would be called 'newe' and the subsecuents of the same block of questions can be called 'newf', 'newg', 'newh', 'newi', 'newj', and so on.
5) Then, I just go again to Tools -> Rename Fields
6) I then rename the variables with the appropiate names as: 'P1103e', 'P1103f', 'P1103g', 'P1103h', 'P1103i', 'P1103j'.
7) Finally, I changed the QES file with the appropiate names and then Tools -> Revise Data File.
This steps worked fine for me.
Regards,