Adding string to a StringValue from another string?

So I'm making a password Gui to open a door, and I've come across an issue which I'm completely clueless on how to do. The problem is, I'm trying to add text from a TextButton into a StringValue, but I can't figure out how ANYWHERE.

script.Parent["1"].MouseButton1Click:connect(function(click)
    script.Parent.Value.Value=script.Parent.Value.Value+script.Parent["1"].Text
end)

Yes, it works kind of.. All it does is add a NUMBER to the Value, and if I try to change the text to a String, it says that it can't be placed because It's a "StringValue".. Keep in mind that I'm new at this but help would be greatly appreciated.