Is it possible to  edit .RWN files? If so, what program would I use?

Quote from Chris82 on 03/07/09 at 10:16:20:

 
Sure, use XVI32
 
http://www.chmaas.handshake.de/delphi/freeware/xvi32/xvi32.htm
 
You asked an open ended question and my answer is perfectly valid. However, I doubt it's what you had in mind. GasGiant answered the question you meant to ask, I answered the question you actually asked.
 
BTW, in my opinion TAS sucks but you can download it for free at:
http://www.addsuminc.com/
or
http://cassoftware.com/tas/index.html
 
Those are the two versions. I don't remember which ISTech uses.
 
Then all you are lacking is the current EvoERP source code. This isn't available so you'd have to have Guido make them an "offer they can't refuse."

As stated, since you have no access to the source code there is no way for you to do this yourself.  
 
However, IS Tech Support offers custom programming services, so it would be best to approach Lynn directly.  
 
See http://www.istechsupport.com/custom.php FMI

Chris
 
I'd like to add that in the past, when I have asked for such minor changes or additions, that may have broad general appeal, Lynn would usually get it done by the next update and make available to everyone on the support plans, for free.