Supernovae play a key role in the dynamics, structure, and chemical evolution of galaxies. The massive stars that end their lives as supernovae live for short enough times so that many are still associated with dusty star formation regions when they explode, making them difficult to observe at visible wavelengths. In active star forming regions (galactic nuclei and starburst regions), visible extinction is especially severe. Thus, determining the supernova rate in active star forming regions of galaxies, where the supernova rate can be one or two orders of magnitude higher than the average, has proven to be difficult. From spectra we obtained of SN1987A, we know that supernovae have emission from a set of 4 strong lines in the mid-ir. These lines include [NiII] 6.63 um, [ArII] 6.98 um, Pf alpha 7.45 um, and [CoII] 10.52 um. The [NiII] emission line is a unique supernova signature, and in SN1987A it was the strongest line in the infrared for a period of a year and a half after the explosion. Since dust extinction is much less in the mid-ir than at visible wavelengths (eg. A(6.63)/A(V) = 0.025), the NiII line can be used as a sensitive probe to detect recent supernovae. In the first ISO call for proposals, we were awarded time to use ISOCAM to observe a selection of infrared luminous nuclei of starburst galaxies to determine the supernova rate in galactic nuclei and starburst regions. Of the two galaxies for which we have fully analyzed data, one of them, NGC5055, shows excess NiII emission centered on the bright starburst nucleus (see Fig. 2). We propose here to obtain a second set of images, using ISOCAM, of our galaxy sample to measure the decay in the NiII line intensity we expect in NGC5055 and any others we might observe in the first set of data, and to enable us to discover any supernovae which might have become visible in the intervening time. A NiII line intensity which does not decay with time might indicate that an excess of Ni has been injected into the starburst region in the past rather than arising from a single recent supernova. ISO is essential for these observations since the key supernova indicator, the 6.63 um [NiII] line, is unobservable from any other existing observatory.