Can someone guide me on how to convert VBA function/sub into a web service.

I have written a heck lot of code in Excel VBA, which works as desired. One of my friends (inside a company firewall) wants to reuse this functionality.
but instead of replicating it in his environment, he wants to be able to use it as a Web Service.

Is this possible? If yes, how do i go about converting vba as a to-way web service i.e. he should be able to invoke it (pass information) and consume outcomes of my vba routine.

thanks in advance.