so if I'm understanding correctly, you have a textbox1 that is being populated with data from a query that you posted, and somehow (you didn't say how) you have textbox2 being populated with the same data, and you want a button that saves changes to textbox2 into textbox1. Begs the question, why are you bothering to go this route? You can "undo" any changes before they are saved in case the user types something in when they aren't supposed to. You could even save the old value into a variable or into an archive table in case they want to undo it after saving, or archive the changes made to the field.
Anyways, to make the text of textbox1 equal to that of textbox2, all you would need is
formName!textbox1.text = formName!Textbox2
that should do the trick unless you're using a "caption" or "label" instead of an actual textbox control. If that is the case, then you would use
formName!textbox1.caption = formName!Textbox2.caption