Iowa ? A district court judge in Iowa has ordered Microsoft Corp. Chairman Bill Gates and chief executive officer Steve Ballmer to testify in person at a trial that starts in Iowa later this month.

The two executives already were on the witness list to appear at the trial, but the ruling means they’ll likely travel to Iowa earlier in the trial to face direct questioning by the plaintiffs’ attorney. Without the ruling, they may have appeared later to answer cross-examination questions by the plaintiffs.

The earliest they likely will be called is January or February.

The company is facing a class-action antitrust lawsuit, which seeks up to $450 million for Iowans who have purchased the software maker’s products since 1994. The case claims anticompetitive practices by Microsoft caused consumers to pay more for its products that they would have otherwise.

Microsoft says its products have been successful because of their low cost and high quality.