This thing you can't do in iReport. You have to generate the jrxml code manually from the java program. First of all read the jrxml file by opening it in any text editor. You can see the various sections into that jrxml. Point out to the <queryString> tag. Just write your query into this place at run time and save your jrxml file. And then do what you want.
Bill, you're better off starting a new thread than to resurrect an old thread that's not even directly related to your question. And even better, start the thread in the "Other Open Source Projects" forum (instead of this one), because that's where JasperReport and iReport are discussed.