Get percentage based on multiple conditions

[Matt]

I would like to determine a percentage in Excel that is based on
multiple conditions. This is for a series of products on different
displays and the quantity on those displays. I need to know out of
all the stores surveyed, what percentage of those stores had a lobby
display with more than 150 cases. If I had a small set of data I'm
sure I could just pivot the data a few ways and be done, but I have
over 50,000 rows. See the sample set of data below for more detail:

Store Display Product Qty
------- -------------- -------------- ----------
123 Lobby Soda Cans 50
123 Aisle Soda Cans 75
123 Perimeter Soda Cans 75
123 Lobby 2 liter 120
123 Aisle 2 liter 200
123 Perimeter 2 liter 50
123 Lobby 20 oz 20
123 Aisle 20 oz 60
123 Perimeter 20 oz 0
456 Lobby Soda Cans 100
456 Aisle Soda Cans 50
456 Perimeter Soda Cans 50
456 Lobby 2 liter 25
456 Aisle 2 liter 150
456 Perimeter 2 liter 25
456 Lobby 20 oz 20
456 Aisle 20 oz 60
456 Perimeter 20 oz 0
789 Lobby Soda Cans 40
789 Aisle Soda Cans 100
789 Perimeter Soda Cans 20
789 Lobby 2 liter 80
789 Aisle 2 liter 200
789 Perimeter 2 liter 50
789 Lobby 20 oz 40
789 Aisle 20 oz 60
789 Perimeter 20 oz 0

From this sample data, you would determine that out of the 3 stores

only 2 of them (66%) have a Lobby display with more than 150 cases.
In Excel 2003, how I can I do this? I cannot wrap my head around it.
Thank you in advance for your assistance.