How can i replace a file ? (Browser -> Invoke Download ?) ?

Hey guys! I have a project with:

Textbox

Button

Browser

So my question is: Can i replace the file?

It's not important what file. For example i press the button and download "save" in my pc a "text1.txt" file.

So, i change some lines in textbox and i press the button again. I don't want to save as a new file, because i will have files like:

text1.txt , text1(1).txt, text1(2).txt, text1(3).txt, etc etc

Need to use other method instead browser plugin? Thanks!