Know-How Exchange : Research/Metrics

I am looking for survey software that I can use to design a survey that includes calculations based upon input. Can someone name a software solution? For instance, I ask the question: How big of an area are you going to cool?
The respondent answers – 1,000,000 sq. ft.

Next question is a Yes/No question which asks do you have a site in mind of about 2,500 sq. ft where the product might be placed? ("2,500 sq. ft." would be calculated from calculating ¼ of 1% of 1,000,000 sq. ft. from the previous question.)