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M dwarf stars are the most abundant stars in the galaxy and have a high frequency of Earth-sized planets comma making them the favored targets of upcoming missions to detect and characterize exoplanets. However comma these stars are known to exhibit high levels of activity and flaring comma which can deplete a planet.s atmosphere of water and ozone over time comma raising questions about the habitability of planets around these stars. It is clear that there is still much to be learned about M dwarfs comma their activity comma and the potential habitability of their planetary systems. Monitoring campaigns with simultaneous observations across a broad range of wavelengths are needed in order to determine how stellar flaring emission correlates across the electromagnetic spectrum. Here comma we propose to conduct such a campaign using HST STIS for four nearby M dwarfs comma spectral analogues of Proxima Cen spanning a range of ages and activity levels. We have already been awarded observing time with ALMA comma Swift comma NICER comma and ground-based optical facilities that will be executed simultaneously between now and October 2022. These HST DDT observations are the only way to add FUV coverage to this campaign. Recent observations of Proxima Cen suggest that UV and millimeter emission trace each other closely during flares comma and this proposed study will show whether this is a universal property of mid-M dwarfs regardless of age. By deriving a scaling relation between millimeter and UV emission comma we will have a powerful new tool to determine the UV environment of stars and their potential to host habitable planets comma and be able to capitalize on existing all-sky cosmology surveys at millimeter and radio wavelengths.