Running one instance of webgl build at a time in a html page when loading webgl builds sequencially.

When embedding multiple webgl builds in a single index.html Page, how to switch between each build and make only one build run at a time?.For example when i click a UI button from build1 which is running in browser and calling c# function with Application.externalCall("jsFunction") to call a JS function in the same index.html page with path to build2.json, but both build1 (at background) and build2 (at front) are running at the same time. Is there any possible way to stop build1 and run only build2 ?