Web Developers → Is this doable?

I work for a small structural engineering company and we typically get calls from contractors and home owners who are building Pole Buildings and would like to get lumber sizes and design information from us.

We have a excel spread sheet that can spit out this information by entering the different criteria of the building. Is it possible to have this on a server with a user friendly interface so that the contractor/home owner can access it online and get the information they need so they they can print out the design information along with construction details pertaining to their Pole Building criteria?

If this is doable, what is needed and how to we go about it?

Yes it is possible. .NET can work easily with Excel data sources. However when it's all done you will realize that you could have done it the right way (database + UI) much easier.

SQL Server Express (Database) on IIS (Web Server) , with ASP.NEt web pages (and business logic somewhere in the C# behind, or be classy, and go with classes to do the "number crunching (business logic)

Totally doable, pretty much like resare said. I recently did a similar thing for a partner company of mine, they have a spreadsheet that calculates values based on some user input and table lookups. I converted the data tables to SQL server and put the logic in ASP.NET C#, and now they can have users access this tool right over the web, without having to distribute a spreadsheet.