I really hope someone can help me....

I am creating a quote form. It is for a roofing company and I want to be
able to create a combo box which lets me select an item, and then in an
adjacent column bring up the dollar value for that selected item. ie.

MATERIAL AMOUNT COST
TOTAL
Colorbond 10m² $25
$250

Under 'Material' I want a list or combo box to select items from. When I
select an item, I want the cost of it to show under the 'cost' column.

How can I do this? Please help...

Terry