generate sound from 100Hz to 4000Hz using c++

what i got is a basic sine wave generator, I will have to modify it so it will generate sound from 100Hz to 4000Hz in 5 seconds.

if(!GenerateBegin())
    return;

short audio[1];

for(double time=0.;  time < 5;  time += 1. / m_sampleRate)
{                 
    audio[0] = short(m_amplitude * sin(time * 2 * M_PI * m_freq1));


    GenerateWriteFrame(audio);

    // The progress control
    if(!GenerateProgress(time / 5))
        break;
}


// Call to close the generator output
GenerateEnd();

any help will be appericiated :D