Free/cheap easy-to-use allow-by-default firewall to block applications

Hello everyone

A little background: I have a program on my computer that legitimately access the internet very, very regularly (a text editor that consults an online database and adds to it), but whenever it does so, it slows down the program. I would like to be able to easily prevent just that program from accessing the internet for a while. The current solution is to simply plug out the internet cable... but then I can't use the internet for other purposes, e.g. receiving urgent e-mails, doing web searches for research, etc.

I have looked at a few free or cheap "simple" firewalls that are able to block applications, but most of them are "block by default", i.e. they block all applications except for a few "major" ones, and then the user has to figure out how to whitelist other programs that the user wants to be able to access the internet. I was surprised that this is the most common way of working, in fact.

Do you know of a reasonably simple firewall (i.e. one that does not involve a dozen steps to block and unblock) that blocks nothing until you tell it to block an application?

Thanks
Samuel

Thanks -- I was aware of it, but I see on that thread that there are commandline options to block and unblock, so it's a one-step process, which would be great if it works. Will try it.