How to create Drop down list to calculate next column

[fray]

How to create Drop down list to calculate next column

i have a column with height with range 10,11...to 20, i want to show that as drop down(how to create drop down?.)
Once we choose the value ie 11 from the drop down it has to calculate (11*Weight) range 20,21.. to 30. and display in the next column

Height Column Weight Column (Height * weight)
Select from drop down 11 11*20=220( this value should display in this column)
11*21 =231
11*22=242
.
..
330 (11*30)

Can anybody help with this.

[hemesh]

Fray Find the attachment.