Research In Motion Ltd. said Thursday it had successfully tested a software “workaround” to keep its BlackBerry wireless e-mail service running in case a judge orders a halt in connection with a long-running patent dispute.

A federal judge is expected to decide later this month whether to issue an injunction against Ontario, Canada-based RIM, which is locked in a legal battle with NTP, a small patent-holding firm in Arlington, Va.

Unless a settlement is reached soon, NTP has said it would seek to shut down RIM’s popular BlackBerry service. The BlackBerry has several million users, including many high-level executives.

Research In Motion said a “leading expert in patent law” from “one of the world’s largest law firms” has supplied an opinion that the workaround doesn’t infringe upon any remaining NTP claims.