Excel Spreadsheet Functions

I want my spread sheet to get all the priceing off of one data source. I.E.

Size Tier
A B C
0 $0.00 $0.00 $0.00
12 $14.00 $12.00 $10.00
18 $16.00 $14.00 $12.00

I want to be able to select one of the tiers out of a combo box and have the entire page refer to that particular tier for pricing. Then i want to have another combo box to select the size and in turn put the corresponding cost into another cell. I am not sure if I am explaining what i want well enough. But if you get it and have a solution please, please email me or answer this.