Why won't the value of this change?

pagenum = ""
local pgnum = script.Parent.Parent.PGNUM.Value
if pgnum == "2" then
	function onclicked()
		pagenum = 2-1
		pgnum = 2
		script.Parent.Parent.pg.Text = "Page "..pagenum..""
		script.Parent.Parent.pg1.Visible = true
		script.Parent.Parent.pg2.Visible = false
	end
end

script.Parent.MouseButton1Down:connect(onclicked)

It's supposed to act like a click change page type thing. You click the right arrow, it changes pgnum to 2, then left arrow checks if the value of pgnum is 2. if it is then if you press the left arrow it will go back to page 1

but the value doesn't change, why?

pagenum = 0
local pgnum = script.Parent.Parent.PGNUM --This is setting the actual value of the value as a variable, not the instance itself.
function onclicked()
        if pgnum.Value == "2" then --This should be inside the function.
        pagenum = "" ..2-1.. "" --Should be a string since you will concatenate it.
        pgnum.Value = 1
        script.Parent.Parent.pg.Text = "Page "..pagenum..""
        script.Parent.Parent.pg1.Visible = true
        script.Parent.Parent.pg2.Visible = false
        end
end

script.Parent.MouseButton1Down:connect(onclicked)