Calculator Project in C#

I need a program that is workable on the web and also can be used as a excutable program to share with my assoicates. Basically what I need is a program that will take into consideration a users input of total debt and allocate that debt to in proportion to a users input for monthly payment. Then once one montly payment has paid down that particular debt the mony will start paying down the next selected debt. Prefereblly I would like this written in C# or VB script.