Auto Completion of Master Sheet from multiple Pages.

Hi, I m stuck on something i never thought i would come across....
I have attached the file for better understanding.

In the file attached, i have a master sheet mentioning different vendors with different type of products.
I have also made separate page for each vendor. I have prepared a drop down list for the products on each vendor page.
Now what i want is, whenever i select whatever product on whichever vendor page, it should effect that particular vendor with that particular product on the master sheet.
For eg. Say for Party Hard drivers, i selected some product, then entered the qty in the cell on their respective page. Then it effects the party hard driver on master sheet with the type of product. In addition, say if i have already made few entries, then all the particular type of product should add up and reflect on the master sheet.

Please revert with help, for any queries plz reply.

Thanks