Ok, I see you want to poll the data instead of push.
Blockly, which is great for simple projects or quick test of a sensor, seems to lack of many functions. It is also not very comfortable for extensive projects and you are required to use a cloud service to edit your code or you have to use a very old desktop version with even less functions. My oppinion about that.
I prefer the Arduino environment. There are many libraries and examples including web servers.
It means a bit more of text coding and less drag&drop but copy&paste from examples work for me well.