Informix SQL ver.2.10 Report Question (HELP)

I would like to write a report and order the information by the outcome of an if statement. example: There are 4 hearing date fields. In the body of the report program I would say: if ba_hear4 is not null then let u_hearing = ba_hear4 else if ba_hear4 is null and ba_hear3 is not null then let u_hearing = ba_hear3 else if ba_hear3 is null and ba_hear2 is not null then let u_hearing = ba_hear2 else if ba_hear2 is null and ba_hear1 is not null then let u_hearing = ba_hear1 NOW: I want to order the report by u_hearing Any ideas?