def _get_recrange(self, f, VXRoffset):
        '''
        Finds the first and last record numbers pointed by the VXR
        Assumes the VXRs are in order
        '''
        f.seek(VXRoffset+20)
        # Num entries
        numEntries = int.from_bytes(f.read(4), 'big', signed=True)
        # used entries
        usedEntries = int.from_bytes(f.read(4), 'big', signed=True)
        # VXR's First record
        firstRec = int.from_bytes(f.read(4), 'big', signed=True)
        # VXR's Last record
        f.seek(VXRoffset+28+(4*numEntries+4*(usedEntries-1)))
        lastRec = int.from_bytes(f.read(4), 'big', signed=True)
        return firstRec, lastRec
Finds the first and last record numbers pointed by the VXR
        Assumes the VXRs are in order