I assume your power meter comes calibrated for the specified frequency range. If you want to waste the money you paid for it, do what others advise.
I would rather spend my money on another power meter for your frequency of interest.
Or, build your RF detector with the frequency response you need. Assuming it would also work at the lower frequencies for which you have the calibrated power meter, you can calibrate your power sensor against it, then use it where you need.
Good power meters are valuable jewels, do not touch their sensors, you will be sorry you did!