Why is this not working?

I'm trying to add a number to a string value when i click a button, but the value wont change on the string value.

GUI.Button1.MouseButton1Click:connect(function()
	a = z + 1
	script.statusv1.Changed:connect(function()
	a = statusv1.Value
		end)
	end)

Change the String Value into a "IntValue".