I have not had to control a LED panel that takes text before.  I have talked with a friend that uses them and I know that he connects them via the RS232 port and sends an ASCII string to the display.  I will try to contact him and see what is involved.  I know it is fairly simple.  I have used the displays that show a value according to the value on an analog signal.  These are generally used to show a pressure signal or some other analog signal to an operator.  It is not what you are interested in.  Do a quick search on google and grab some manuals from the sites you find.  Information on how to connect will generally be available.  You might even find that AB sells a display.   I found a manual of a typical display here:

http://www.hitechled.com/images/tutorial/Allen%20Bradley.htm#_Toc497896823

I looked through it and there are various ways to display the text on the display.  Check it out and I think it will clear a lot of things up.

Got the program you sent - should have let you know earlier but been slammed. lately.  I looked through it quickly and you took what we talked about and kept going!   Have you hooked it up and tested it yet?