To. Ashok :
You have not yet signed any agreement as of now.
1. A agreement is for "positive" performance of doing an Business.
Hence any restrictions placed for "negative" performance would be violating the purposes of Contract Act. There is always a Contract rescinding option open to either of the parties and violating of such rights is bad agreement.
THIS IS HOW YOU CAN PREVENT "B" FROM SELLING GOODS TO "C"
2. However, a "MOU" can be executed between "A" & "B" for doing "positive" performace of selling "B" party goods routed soley thru "A" party only, for so and so duration, subject to specific amount of business quantum committment by "A" to "B". MOU may also contain "positive" provisions of doing sole business in specific areas of districts, i.e. sole-selling rights.
3. The "MOU" may contain a "positive" performance clause stating that IF either parties violate the terms and conditions of the MOU, the parties shall pay to the other a specific pre-determined amount of compensation.
There are many other parameters that are used typically in MOU, for such type of business activities.
Keep Smiling .... Hemant Agarwal