replace a word in a text file with what somebody types in

I need to replace a word in a text file with what I type in in a display dialog box. Basically it’s an FPO file that tells my application where to drop the FPO files. But it is going to be different for every job seeing the FPO file is stored in the job folder. Here is how I set up a job folder…I have an applescript that wiil ask for a job number and then a customer name. It makes a copy of a master folder on my server and renames it what I put in for The number and name. I need to have the FPO text file point to a folder that is in the new one I just made. So I’m thinking I can use the variable for the number and name that was put in and just replace some text in the text file with it. Sorry for being long winded…

thanks,