XThreads input value into global user value

[Lilz]

Hello o/

Is it possible to write XThreads input value (for example {$GLOBALS['threadfields']['mykey']}) into value assigned to specific user (author of post)?
I need only one value of 'mykey' at time, so its ok to overwrite it. I also want to make this value easly to change with every post, so thats why I dont want to use custom profile fields (cause it takes so much time to go to profile editor, save changes and then go back to topic).