Coupon for 'first 3 months free' subscription - is it poss?

[21inspired]

Working with s2member Pro.

We are setting up a new site where members pay a monthly subscription.

We want to set up a coupon code which some people can use to get: '3 months free' subscription.

Is this possible with s2member pro? Any ideas how to set it up

If not 'out of the box', would it be possible with some custom hooks?

Thanks,
Roger