Using ATMEGA flash memory to log data


I was hoping to use the Arduino’s own flash memory to log data from a sensor.
Is there any way I can do this? SRAM does not have enough memory for me to add data, and the PROGMEM attribute is only for constant data, I can’t declare a space of bytes reserved for one type of sensor, for instance, because later I cannot change this,.
Is there any way this can be done?

Thanks in advance

Yes, check this out

Please let us know if you get it going the way you want and make a how-to guide.