How do you use an IF statement that checks to see if a file exists. I am running a program that starts automatically grabs the filename and path based on the current drawing's path and extracts information from it. However if the file does not exist I get the following error
Initializing...bad argument type: FILE nil
I would like to avoid having the error message show up, maybe a message similar to the following to show up on the command line only

X5505.txt does not exist

Lisp routines dont seem to like it when they get an error, they stop running all together, and that makes the stuff that might follow this command not load.

Any help would be appreciated.