Click-to-Call TAPI Compliant Explorer addin

We're looking for some pointers on how to do this technically. Does anyone know of an add-in for Internet Explorer that will identify phone numbers displayed on a web-page and allow that number to be clicked to initiate a call? We need to hook up to Avaya IP Office, which is a TAPI compliant PBX system. If anyone has done this with IP Office or any other PBX, which addin did you use and how successful was it? Any advice gratefully received. Cheers, Graham.