Yes, I forgot to mention that. Thanks Lionel

That above string just error's when I enter it into my calculator. Maybe because its running in a coroutine.

Oh, so it will become even become better \o/
Thanks for enlightening us

Why 3?
It was a cool way of fetching external data

Ah, didn't know it could be disabled. Thanks

Well, it really depends how you want to do it

First create the class and its init script. The init script for a button would set for example it label and size. Then you need to add an paint function to it, were you draw it.
Also, you should keep a table with references to all the buttons, so that you can link event to it.
Something like this:
--The table we keep all references to created buttons in
ButtonTable = {}

--Create the class
button = class()

--Create and init the button
function button:init(label, x, y, action)
    self.label = label
    self.x = x
    self.y = y
    self.action = action
    self.labelWidth = 0
    self.width = 0
    self.height = 20
    
    table.insert(ButtonTable, self)
end

--Draw the button
function button:paint(gc)
self.labelWidth = gc:getStringWidth(self.label)
self.width = self.labelWidth + 4
gc:setColorRGB(0,0,0)
gc:setFont("serif", "b", 12)

gc:drawRect(self.x, self.y, self.width, self.height)
gc:drawString(self.label, self.x+1, self.y+2, "top")
end

Well, but now you will wonder how to make it clickable and all.
Look at this full code:
--The table we keep all references to created buttons in
ButtonTable = {}

--Create the class
button = class()

--Create and init the button
function button:init(label, x, y, action)
    self.label = label
    self.x = x
    self.y = y
    self.action = action
    self.labelWidth = 0
    self.width = 0
    self.height = 20
    
    table.insert(ButtonTable, self)
end

--Draw the button
function button:paint(gc)
self.labelWidth = gc:getStringWidth(self.label)
self.width = self.labelWidth + 4
gc:setColorRGB(0,0,0)
gc:setFont("serif", "b", 12)

gc:drawRect(self.x, self.y, self.width, self.height)
gc:drawString(self.label, self.x+1, self.y+2, "top")
end

--What happens if you click the button
function button:click()
self.action()
end

--Check if clicked, and if clicked call its click method
function button:checkClick(x, y)
if y >= self.y and y <= self.y + self.height and x >= self.x and x <= self.x + self.width then
self:click()
end
end

--Check ButtonTable, and draw all the button in it
function drawButtons(gc)
for _, selectedButton in pairs(ButtonTable) do
selectedButton:paint(gc)
end
end


----------------------


--The on.create even. Here we create a sample button, and make that it will call testFunction when clicked
function on.create()
button1 = button("Test!", 100, 50, testFunction)
end


--TestFunction
function testFunction()
bclicked = true
platform.window:invalidate()
end

--The paint event
function on.paint(gc)
if bclicked then
gc:drawString("The button was clicked", 10, 10, "top")
end

drawButtons(gc)
end

--Link the click event to the buttons
function on.mouseDown(x, y)
for _, selectedButton in pairs(ButtonTable) do
selectedButton:checkClick(x, y)
end
end

This should explain most of it
Note that I didn't try this, so there might be some errors.

I strongly recommend you too look at the source of Adriweb's contest entry here: https://github.com/adriweb/Nspire-BreakOut .
Its a very good example of what you want to do, and should be easy to understand

EDIT:
Ok, tested it and fixed some bugs (Thanks Adriweb!)

Looks nice, good job