attributes for selling "per square foot" items

[virtualahmad]

i have a product which is sold based on the height and width (banner sign printing) dimensions and charged by square foot dependent on the material.

I would have an attribute called material which would be either drop down or radio buttons and list Material A - $4.99 /sq. ft., Material B - $10.99 /sq. ft.

I'm looking to create 2 text attributes called Height and Width, and ideally calculate based on that.

Seems obvious this isn't built in...

so i'm looking for alternate suggestions.

I thought perhaps if i made a text box called "Total Square Feet" and the user types in "20", it would be 20 x the price of the material. But i'm at a loss as to how that would work.

Any suggestions or recommendations ?

[kobra]

If always in even feet I would select one dimension - either height or width and then have the other selectable or the entered value or ie:

By material
select "A" or "B" (4.99 - 10.99)

by attribute:

2ft high - enter ft wide
3ft high - enter ft wide
4ft high - enter ft wide
etc