How to restrict shopping just one manufacturer at once??

[pcolomes]

Hi.

 

This is my first post here so i' sorry if this has been answered before (yet better).

I need (very urgently) to know how can i restrict shopping from my catalog by one manufacturer at once.

 

I mean, i have a list of manufacturers wich sells a lot of different products, but actually i can complete my shopping cart with different products from different manufactures and i need to be restricted so i can complete my shoppping cart ONLY with products from a specific manufacturer.

 

For example

 

My cart now:

1 Pendrive (Manufacturer: Kingston) 512 MB: $10
3 CD-ROMs (Manufacture: Sony) 700 MB: $5

Total: $15

 

But i need to show only this:

 

 

My cart now:

1 Pendrive (Manufacturer: Kingston) 512 MB: $10
ERROR: YOU HAVE ACTUALLY SELECTED Kingston PRODUCTS. YOU CAN ONLY BUY PRODUCTS FROM Kingston.

 

 

I hope you can help me because this is absolutelly indispensable for my business.

Thanks in advance and sorry for my bad english.

[pcolomes]

Or maybe restict shippings only to an exact number of manufacturers?