Quark 5 find and replace but with a twist

Hello - how can I applescript Quark 5 to find and replace a list of any characters to a different set of characters? Here is what happens:
our PC server changes foreign language letters to a certain other character and I am wanting to run the document through an applescript so that whenever say % is found it is replaced with ü - Any suggestions on this one?
Thanks
Jim Robidoux
Business Card Express