FFT - radix 2 - decimation in time -frequency range
If you studied the materials I recommended you on comments to your previous question. You would notice that FFT algorithm takes advantage of certain symmetries to make computations faster. If you don't want to work with a whole frequency range simply select the appropriate sampling frequency and concentrate all your FFT resolution points there. If you can't choose your sampling frequency take the samples and then decimate  them. Alternatively you can also use the Goertzel algorithm to work only with the frequencies you select.