Hi,
You can achieve using local variables.
Wne your screen loads:
UpdateContext({varEnableCB: false})
On your button click, with your other commands, paste this as your last command
UpdateContext({varEnableCB: true})
Finally, on the visible property of your checkbox
varEnableCB

This will make sure that when the screenloads, the checkbox is invisible, when the user hits the button, the checkbox becomes visible.
Hope this helps.
Thanks.
Warm Regards,
Irfan