I am planning to make dc/dc boost converter working in 5kHz , can anyone help me how to change the duty cycle from 5% to 90% . can you help me with the code in IDE or in MATLAB or even in simulink.

The analogWrite function sets the duty cycle of a PWM output. The default PWM frequencies are around 500 and 1000 Hz. Changing the PWM frequency is a subject often covered in the forum, so a search should find how its done.

Wawa:
delayMicroseconds(100-60);
That also isn't allowed.

Study the reference page on the learning tab here, or in the help>reference tab of your IDE.
Leo..

Now I'm confused (and I did read the reference page )

delayMicroseconds takes an unsigned int; both 100 and 60 fit in an unsigned int; the result also fits in there.
The maximum value for an accurate delay is 16383, so that requirement is also met.

I am still working on it , actually I need it in matlab to use a fuzzy logic controller to control the boost converter by changing the duty cycle. the working frequency is 5kHz.