Woocommerce Kilograme base price PLEASE HELP

Dear all,

Please any one can tell me that how to add dynamic prices based on product kilograme?

In the product administrator I’ll assign something like 10 Kg = $100.
So in the site when customer enter 5 Kg in a text box then it should auto calculate the price($50) & the calculated price should go to final cart.

Please help me & sorry for my poor English.

Thanks

Karthick