I have little or no web coding experiences so am asking for a freebie from those more in the know- you guys

Looking to create a small applette that will allow a user to determine the CFM(cubic feet/minute)needed for our particular product line.
1.User would enter a particular model number(or drop down)
2.This would pull from a DB or spreadsheet(which is built) a factor number(in this case a square ft number based on the face opening of our piece of equipment LxW/144)
3. User would enter a required operating rate for their face velocity.
4. Number of cubic ft/min would be dispalyed in an answer box.

ie
we make a product(model xxx1) that has an opening of 32.14"Wx7.5"H=241/144=1.67
user wants to operate at a required face velocity of say 112
which works out to 187.4833

they would type in(or choose from a drop down) the model
xxx1, enter in a Face Velocity value(112 in example), and the applet would show them the required CFM to achieve that.

Anyone care to throw me a small bone to get me started-would really appreciate it