Contract: commissions and dismissal?

Hi,

Background:

I work in the robotics industry, and sell automation solutions with robots.

I typically work 9-12 months on a contract, and once signed there are various payment milestones spread over the full implementation:

(as an example)

1. down payment 20%
2. delivery of goods to site 30%
3. first successful trial run 30%
4. final acceptance 20%

The implementation from contract to final acceptance easily takes 12 months.

Commission setup:

Based on the contract value, a certain commission percentage is awarded.

BUT...payment of the commission only happens after payment of each milestone.

So I would get 20% of the commission after payment of the down payment, then 30% after payment for the delivery of goods to site etc.

I assume you understand the system as it's pretty straightforward.

Problem:

If I would resign, I can understand I would not get paid the future commissions on that contract.

But the risk is that the contract gets signed, and I get dismissed after the second milestone for example.

Question:

What to add to my employment contract to avoid this issue?

I was thinking 'commissions will be due after dismissal'?

But I am not sure if this is common practice?

Should it be limited to wrongful termination only?

Does anyone have experience with this?

Or suggestions?

Thanks a lot!