GUI Text Input?

So i am trying to figure out how to detect a certain text input from a user like lets say

plr = game.Players.LocalPlayer
plrgui = plr.PlayerGui
websites = plrgui.NNet.Domains
oops = plrgui.NNet.Notices.Error

if input == "www.whatever.com" then
	websites.whatever.Visible = true
else
	oops.Visible = true
	wait(3)
	oops.Visible = false
end

I have no idea how to receive input from a text box.

So my question is:

How can we have a "local script" that checks input from a textbox and if the text is correct it will then return into showing the proper gui?

TextBox's have a FocusLost event which fires when someone has typed something into a textbox. So if you want to recieve input, you would do this:

local TextBox = script.Parent.TextBox
TextBox.FocusLost:connect(function()
	input = TextBox.Text
end)

Basically, everytime someone has finished typing something into the textbox, the input will be whatever the Text is. Hope this helped!

Note: For more information on FocusLost, click here: FocusLost

local plr = game.Players.LocalPlayer
local plrgui = plr.PlayerGui
local websites = plrgui.NNet.Domains
local oops = plrgui.NNet.Notices.Error


isValidURL = function(url)
	local valid = false
	local site

	for _,v in pairs(websites:GetChildren()) do
		if string.lower(v.Name):match(string.lower(url)) then
			valid = true
			site = v
		end
	end
	return valid,site
end

script.Parent.TextBox.FocusLost:connect(function()
	local url = script.Parent.TextBox.Text

	local valid,site = isValidURL()
	if valid == false then
		oops.Visible = true
		return
	end

	site.Visible = true
end)

This is un-tested and I'm at school so IDK if it works but that might help a little bit!