Diagnostric web tool

Need to have a system where the user get one and one question (in total 100 or more)to tick off Yes/No. A number of known causes of the problems /diseases are described with corresponding symptoms. Each symptom must be able to "weight" (give a numerical degree of relevance or importance) the symptoms related to the various diseases: For instance "Coughing at least 10 times an hour during the last 14 days" will be weighted as 10 for Tuberculosis, but only 2 for flue. The setup must be ready made and installed on a server. The back-end user must be able to insert new symptoms and diseases, and give them a weigh. The front end users must be able to tick of all the questions, and be given a list of the 20 most likely causes of the problem / disease.