Web Application Asp.NET

I have developed a Google Maps application using ASP.NET and JavaScript that allows the user to add a starting address and a destination address in order to view the gas stations that are on that route. The target of this application is to show the gas stations on that specific route to the user. The coordinates and addresses of all gas stations are stored in a database. What I am having difficulty with is producing a solution which allows me to show only the relevant gas station markers and to hide the markers that are not relevant. Also i want to mark the cheapest gas station in the route. Relevant, in this context means, on the specific route selected. So, all gas station markers not on that route, should be hidden. In the attached image is a visual example. A is the starting point and B is the destination. Along the blue line, the route, I would like to show the gas stations only between A and B. Any gas station that isn't within A and B should not be shown.