I got an email question from someone learning about options. They asked me "wouldn't the max pain strike price within the expiration time frame be a variable value?"
Max pain may change from day to day. You'll find it happens often with the weeklies. Especially after the stock makes a large move.
Max pain is based on the open interest. All publicly available open interest data is posted only after the stock market close. You get one max pain figure for the day and it will stay there because open interest data isn't updated until the next day.
Intra-day you can try to determine direction from the volume charts (volume data is published intra-day). But remember that you don't know if contracts are opening or closing when you look at volume.