Formula needed for my parts list
 

I have a parts list with many different parts numbers in a column. Each
unique part number has different prices according to how many parts are being
purchased, within the same row.

I want to make a column that calculates the price for each unique part
number, according to which price has been chosen from within the row. So i
want to type a formula that says "multiply this number of parts by this
price" where the number of parts will have to be manually inputted for each
part, and the price is chosen by simply clicking on the cell which contains
the correct price. There will be a range of cells with prices, and the
"correct" price will be in a different column depending on the part number.

Is there a way to define a range of columns and tell Excel that within each
row of this range of columns, one cell will be clicked, and i want it to
highlight that one cell permanently (unless another cell within that row is
chosen), and automatically know to use the price within the chosen cell for
the calculation?

A bit confusing to explain. Ask questions if you need a better description
of what i'm trying to do.

Thanks!