I am a foreign individual who will work as a broker for a China-based
supplier. I have one customer/company located in California who wants
to buy from me.
The ideal transaction for me is: 
- The customer places the purchase order with me. 
- I forward the po to the factory. 
- The customer sends money to the factory's account as down payment. I
will eliminate the downpayment in the future.
- The factory makes the order and ships it to the customer. 
- The customer sends the rest of the payment balance to the factory
before he receives the original import documents from the factory in
order to do the custom clearance.
- The factory transfers my commission to my bank account. So, the one
who pays me is the factory, not my customer. What my customer pays is
the final price, the factory's selling price plus my commission.

I am trying to protect my interest by NOT allowing my customer to
contact my supplier directly and buy from the factory directly WITHOUT
paying me any commission (6% of the total transaction).
If the factory contacts my customer directly, and the customer buys
from them, the customer still obligates to pay me a commission of 6%.
If the customer breaches the contract, they're required to pay me $2,500,000.00. 
The term: 5 years 
Law: this agreement should be governedby the laws of the state of California. 

Is it possible to create this kind of agreement?. 
Please, help me in giving me many samples of this kinda' agreements
(including the links) and your comments / suggestions. I don't know if
this venture is gonna work or not but I will give it a try.