1. First, prepare the sample table.
Inserting a drop down list
2. In any cell create, a drop-down list to choose the products from sample the data you've just created. Use data validation for that.
3. Click on the cell right next to the drop-down list.
Vlookup formula to autopopulate a list
4. Write the formula =VLOOKUP (value you are looking for, table array, column number, false).
4. If you can't write that formula, just copy/paste mine: =VLOOKUP(E3;B3:C10;2;0).
5. Your spreadsheet is complete:
Here you can download this spreadsheet for free.