Daimon! Has anyone done this for you yet? I had a go - seems to work.
Add this to the end of Main.Lua
Code:
prog.ppWin:SetWantsKeyEvents(true)
prog.ppWin.KeyDown = function( sender, args )
if args.Action == 0x100000B3 then
prog.ppWin:SetVisible(not(prog.ppWin:IsVisible()))
end
end
Call it a late Christmas present *grin*